Presoak is 60/120sec . BUT ONLY IS NECESSARY IF YOU ARE INTERLEAVING A STACK OF FILM. At no other time do I presoak, sheet or roll film of any kind.
Fred Picker is the one who wrote up the procedure with the wedge, presoak, pick up stack, fan out, move one sheet at a time to the developer, push into developer emulsion side down, when you get them all immersed, pick up the one from the bottom of the stack and place it on top changing direction so you know when you get to the end. Keep cycling for 60 sec.
After 60 sec, cycle thru the stack again, rest for balance of 60 sec, repeat for remainder of developer time.
I used to run multiple developer trays with a single sheet in each. A 5x7 tray is sufficient for 4x5. Lift 1/2 " and drop two adjacent sides for each cycle. Two cycles will let you work around tray.
You can use a tape player to time or an audible electronic timer. I have the timer on a shelf above the developer trays with a piece of fogged film over the lights and a baffle such that no direct light hits the trays. The film is fogged enough so that you have to get really close to read the clock after your eyes are dark adapted for 5 minutes. Still no direct light should hit the film.
Further I put an opague cover over the trays.
The first post was a bit sloppy as I was working against a deadline.
http://www.freestylephoto.biz/hutchings.php
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I take no personal credit for this and only relate what they have published. I will say the methods work, specially Gordon`s.
Google to find out more about these masters.