Far as I know yes you can use the same dip for mulitple birds and if I am not mistaken use the same dip for 5 days check the instructions on the package. That is the reason for cleaning the feet prior to dipping, to keep the solution clean as possible. Also I might try and break down to 1/2 gallon and put in sm container. Only because I am very frugal.
I have read on here people doing the quart size so I am not the only one. This stuff is not cheap IMO but if it works would be worth it's weight in gold to me. Just make sure you use Distilled water I also read not such good results with tap. Something to do with minerals or chemicals in tap water that is counter productive.
Good luck!

Good luck!