Note: This is another in my sequence of post-Mystery-Hunt cryptics, which started with "Still There," "Post-Game Predictions," "The Sequel," "Power Lines," "A Lesson in Cryptography," "Yet More Villainy," "Further Escapades," "Time X*X," "Honeymoon in Segas," "If At First You Succeed," "Another One From The Vault," "Next Winter: Wonderland," "DAB," "Some Extraction on the Side," "Another Campaign," and "Mind The Sharp Bits!"; this one was written before the 2020 hunt and refers to the 2019 hunt. "NI2" and "NI3," as is usual in the National Puzzlers' League, indicate the second and third editions (respectively) of Merriam-Webster's New International Dictionary.
Alas, your map of the Holiday Forest was incomplete; the hidden intertown path we're on is still covered in molasses. Can you help? The following information may be useful:
Getting Started. The wordplay in each of 16 clues yields a letter string with one incorrect letter; where it is the string's pth letter that is incorrect, underline the clue's pth word (a hyphenated/apostrophized expression counts as one word). The first eight such words (in clue order) will be an ambiguous cryptic clue for 1 Down that might clue either one of us; the last eight will be an unambiguous cryptic clue for 10 Down naming the town at one end of the path.
Facilities. Reflecting the ambiguity in 1 Down, six entries intersecting it have "double-definition" clues where the two definitions define answers differing in their first letter (tagging may apply to either answer). When you enter their answers, put both first letters in the intersecting square in first-definition-last-definition order, forming a "bigram" (two-letter sequence); one of us will use the left-hand letters in these six bigrams, and the other the right-hand letters. In six other clues, a bigram in one word must be replaced by one of these six bigrams before solving; the replaced bigrams, in top-to-bottom order of the bigrams replacing them, will name the facilities where we've researched how to handle all this molasses.
Procedure. The answers to 15 clues must be altered before entry, five in each of three different ways, to present our three-step procedure for doing this cleanup (three altered entries are capitalized, referring to a city, a person, and persons):
Path. The remaining 12 answers form six intersecting Across/Down pairs that conflict at their "special" intersecting square; one answer requires one bigram in that square, and the other requires a different bigram. (The same two bigrams will be involved in each conflict, which will depict the event from (i) above.) You can now draw an almost complete map of the path, starting in the letter from 10 Down that has the highest Scrabble™ value, and proceeding by rook moves to visit all the special squares.
For each of these 12 entries, where its special square is the rth square from the start and sth from the end of the entry, circle the rth letter from the start and sth from the end of its clue. Then proceed along the path; as you enter or leave a special square, read the circled letters for the intersecting entry you are moving parallel to — rth-then-sth if you are moving "forwards" (right or down), sth-then-rth if you are moving "backwards" (left or up). The resulting 24-letter sequence will say what each of us is (which qualifies us to assist in this endeavor).
Finishing up. To see where to go to complete the path (and where you could find other qualified assistance), apply the three alterations from Procedure, in order, to its (ii) phrase. Change the symbol there to its opposed symbol to see what town you have reached.
1. Alda and Swit show ROTC to fawns and horse
5. Substances containing nitrogen and americium before day thirteen or fifteen
8. Wood filer with low-class airs
11. Joints hidden by the bottom of one's tons of silk finally observed in a mirror
12. A term meaning "having many a theatergoer's hairstyle"
14. Awkwardly scampers with Times journalists' equipment carrying flashbulbs (2 wds.)
16. Snow area that includes Cardiff's low-lying, wet regions
19. Took money in exchange for muscle in your ear
20. Is starting to list drinks, little by little
21. Last of Esperanto poetry, while one-dimensional, is spicier than typical [NI2]
22. Coin-producing facility is apparently cool plant
23. What rabbits may be doing to carrots is completely gratifying
25. Ratiocinate to figure out fish can swallow Volt
27. Is "bovine" spelled backwards the word put before a Mozart opera's "fan"?
28. Men that stand beside knights and food preparers
29. Nonstretchable quality of cilia isn't yet changeable
31. In court, gutlessly says word preceded by meno to mean "not so fast"
34. Where you catch trains in French waterway that flows through Bern
37. Oceanic motions caused by Luna and Penny wearing cravats
38. Piece of hosiery carried by insect to rotating vessel filled with laundry [NI3]
39. Use mace to cover rot-encrusted game alongside strange egglike entities
42. Unsettled, outspoken Parisian at the Ivy League school
45. In no way repaired support with its top ripped off (2 wds.)
46. Pertaining to Dawn's temporary extension of funds [NI3]
47. One (as a general rule) venerates Haile Salassie, Spanky, or Darla endlessly
48. Mostly Urdu packaging secondarily misdescribes chicken or duck
49. Not near west UK fliers who are military and adult
50. He's making Charlie too upset — they get into Moxie and Hires
51. Right after this one sequence of letters and other symbols
52. Gyrating, noseless, long-legged birds make noise as they slumber
53. Not very colorful way to capture disheartened Sasquatch
2. Stop daydreaming about Pan obstructing Loki when topless
3. Red stripped, donning Q & M's edgiest bits of clothing
4. Watches, leeringly, less good Cheers
5. Saw ages corrupt an African spear's name
6. Jason's wife and the author of Romance answer
7. Game official that's cute flipped over a bit of Necco candy
8. Tree line north of pair of antelope
9. Schmo that's cleaned out 12.5% of schmaltz bottles the Venetian puts schmutz into
13. A bed containing one's anorak or ulster
15. Give nude somersaulting a go at last, later
17. Article on tuba describing small-time attorney-to-be's exam (abbr.)
18. Looks south at clothing from Erie & Vegas
24. Rudy, in comparison with Sol, presents wilder rants (2 wds.) [NI3]
26. Unsuited to varied works in which recorded images may be shown (2 wds.)
30. Acts like a trader of second-hand climbing shorts, at first
32. Leaves sixty tees to support two items from Spalding
33. Fly from Goa's funny
35. Roused people in a soda ad wanted to buy the world this
36. Sound heard before MGM films featuring unenergetic dog
40. Identifying names Mr. Arnaz originally gave Chad, Jordan, and so on
41. Expert ignoring Dutch or Italian currency symbol becomes chief
43. Fourth installment of Celebration Time™ results in accusation in the Senate (2 wds.)
44. A tetrad of opponents like the other spelling of "turbanned" (hyph.)
45. A coxcomb's final poem written to praise a house