OK, I learned tank processing in 1967. Only did it a couple of times after that segment of the investigative school I was in so take it with a grain of salt. Anyone who is doing it more often and recently, correct anything I say wrong.
I don't remember being told to put film in emulsion side up or down. I was told to be sure to get each film completely in the developer before inserting the next. Otherwise if you try to put more than one in at a time they will sitck. They make a heck of a loud noise when you pull them apart, and it doesn't do the emulsion any good either. Luckily the room was dark so only those close to me had any idea who it was. 😀
They shouldn't touch the bottom of the tank, since by the time the emulsion is that soft, you should be moving them from bottom to top of each other, which should mean you have your hands under the stack. Tray developing requires some practice but is not difficult unless you run into the allergy problem some people have.
I have never seen dip and dunk film holders, but they must exist. You could try an ebay search if you choose to do it that way. I never learned that but hope to some day soon.
I have 9x12 backs for my 4x5 camera. I didn't know that you could put 4x5 in 9x12 holders (without cutting it down, which I have done both for 9x12 backs for the 4x5 and for straight 9x12 folding cameras.) since they are so much smaller.
Anyway, good luck and enjoyment.
