I just ruff scuffed the old silver colour paint with 800G then just tacked it...but four years ago, if I remember correctly I used about about 120G on the ugly pitted chrome "all over" so the paint would hold (and it did very well). Think I used one can for each bumpper to get a good base. And yes, I would think acetone would work very well.
PS Dupi-color now has a spray primer out that's made for a "chrome" surface to hold the paint on.
That's about all I can tell ya! ...because that's all me knows mate!