Well a dark room with table and comfy chair is best scissors and reloadable spools.
If you have plain plastic spools you will need to stick on the tape in daylight to spool with bulk reel still in can. This is a good party trick.
Forget 42 unless you are using PET and have the special Ilford 72 tank and manual counter on camera like a Leica M2 which keeps on counting past zero...
try for 36.
If you don't like losing three frames with a Watson or other tear drop you need a changing bag as well as loader.
snip film with 1 inch protruding from trap attach spool and cassette.
zip into cbag open trap of loader seat cassette push in winder close light trap and loader door unzip bag, open light trap wind on 41 or 42 frames.
This should protect the 36th frame or 37th even with a small camera, but it is best to stop at 35.
It does need concentration. Id not bother cept if you are using short ends or special film.