I can't really remember the minimum number of players that you have to use to avoid a 25-0 forfeit. I think 3 is correct, but don't trust me on this one; definately need someone else to confirm.
One thing I know you can do is buy some horrible players to fill minutes during your scrimmages. If you want, you can even buy a couple guys for $1000 each, use them for the scrimmage, and then fire them before the financial update on Monday. The overall cost of doing this is extremely low, and I just thought I'd mention it as an option.