Just wondering could you expose say 10 screens in a row set them aside and take them all to the washout booth which isn't in a light safe area to wash out instead of going back and forth for each one.
by not light safe, are you saying out of sunlight but under florescent lights? If yes, I would just stand them vertically each one up against the last and not worry too much about it. If something other than florescent lights, you might want to rethink that.
However, I would prefer doing them one at a time as I like to know where to expect the image to start washing out.