Lots of good advice -- developing B&W sheet film is a simple enough process that there's plenty of room for variation. If it were me...
I'd start by processing the first few sheets one at a time until I've convinced myself that I've got the basic process down -- developer time, stop, fix, wash. In my experience, most scratches on film are a result of a corner of one sheet dragging against the surface of another while they're being shuffled, or in washing, so just sloshing one sheet in a tray, emulsion side up, really minimizes the chances of scratching.
Once I have some nicely done negatives under my belt, I'd process two films together in a tray. I would process them face down because, in my ugly hands, I get fewer scratches than I get with the emulsion side face up. Your mileage may vary! Once I manage to eliminate scratches with two sheets, I'd go to four sheets at a time. With four sheets, I'd want at least a quart of developer in an 8x10 tray in order to have sufficient depth of solution to help prevent scratches. You can probably use less solution in a 5x7 tray but I wouldn't know as I don't have any 5x7 trays. I use one quart because the T-max film I use really, really likes FRESH D-76. I mix D-76 a gallon at a time and as soon as it's mixed, decant into four one-quart bottles, filled to the brim and tightly capped. D-76 keeps for a long time that way. A quart of D-76 will develop 16 4x5 films, so I try to hold off processing until I have about that many sheets to process, but that's just me, 'cause I'm cheap. I normally process 8-12 sheets at a time but I've been doing this long enough that I have lots of practice. The more practice you get, the better you get at it, the fewer scratches you'll have, and the more sheets of film you can process at once. Good luck and have fun!
Mike
I'd start by processing the first few sheets one at a time until I've convinced myself that I've got the basic process down -- developer time, stop, fix, wash. In my experience, most scratches on film are a result of a corner of one sheet dragging against the surface of another while they're being shuffled, or in washing, so just sloshing one sheet in a tray, emulsion side up, really minimizes the chances of scratching.
Once I have some nicely done negatives under my belt, I'd process two films together in a tray. I would process them face down because, in my ugly hands, I get fewer scratches than I get with the emulsion side face up. Your mileage may vary! Once I manage to eliminate scratches with two sheets, I'd go to four sheets at a time. With four sheets, I'd want at least a quart of developer in an 8x10 tray in order to have sufficient depth of solution to help prevent scratches. You can probably use less solution in a 5x7 tray but I wouldn't know as I don't have any 5x7 trays. I use one quart because the T-max film I use really, really likes FRESH D-76. I mix D-76 a gallon at a time and as soon as it's mixed, decant into four one-quart bottles, filled to the brim and tightly capped. D-76 keeps for a long time that way. A quart of D-76 will develop 16 4x5 films, so I try to hold off processing until I have about that many sheets to process, but that's just me, 'cause I'm cheap. I normally process 8-12 sheets at a time but I've been doing this long enough that I have lots of practice. The more practice you get, the better you get at it, the fewer scratches you'll have, and the more sheets of film you can process at once. Good luck and have fun!
Mike