Bob,
I haven't got it down to a science. I've used 5 gallon home Depot buckets with two cups powder and de-rusted front spindles, brake caliper assemblies, backing shields, all the bolts and hardware and now I've got two upper control arms in the same solution after those parts. I basically spray parts with degreaser, take to carwash and power wash, then in the bucket they go. Sit overnight, scrub with scratchpad, rinse, dry, put on protector then ready to store for future restoration steps. It won't affect paint, but does cut grease and grime along with rust. I did my whole rear end housing in a 42 gallon trash can and @ 4 cups of powder. Came out amazing and didn't have to worry about chemical hazards of other products.
Hope that somewhat helps.
Dan in Kansas