Steve, the can says 1 can to a quart. That's what I do, although I usually mix a pint of paint and a half can of hardener.

I don't mix it to the acetone, but to the paint.

I add the hardener to the paint, and then thin with acetone.

No set ratio of paint to acetone. I thin to the consistancy of milk. I probably start at 2 parts paint, and one acetone. I test spray, and add more solvent,if necessary. It could easily end up as a 1:1 mix.