Acetone, Goo Gone and elbow grease did a wonderful job on the junker Shoestring I rebuilt. I can't swear it was Rustoleum though. But the acetone took it right off and didn't seem to faze the hard clear base coat, whatever it was. She's a beauty now, other than a few patches of pretty I've knocked off of it. It was heavy Yellow from nose to tail and I stripped it in about a week of evenings doing detail work
Rusty
Before and after: