I've been painting plastic models for years, and would NOT recommend using any type of harsh chemicals like acetone or lacquer thinner to remove paint!!!!! The plastic will melt like a snowball in August. You'll be left with a puddle of goo. Rustoleum takes a long time to dry, and a week is about right. Give it some time, and don't try to over coat it with any other type of paint other than other Rustoleum colors, or water based kinds. In the future, test the paint on a small inconspicuous portion of the plastic, like a spot on the inside. There are few paints avaialble any more for models, so beware. I used Floquil colors for years, but they're not being made any more. The modern acrylics are OK as are the Testor's Model Master lines.
Read the labels carefully. If the paint contains any sort of acetones. ketones or lacquer thinners DON'T use it on plastic! Even Scale Coat will harm plastic if you use Scale Coat I. Scale Coat II is formulated for plastics.
With any kind of rattle can paints, try to develop a soft touch, using as little paint as possible in thin coats. Let the coat dry to the touch before attempting more coats. I's like the old joke: "How do you get to Carnegie Hall?" "Practice, practice, practice!".
I second everything here, including just setting it aside for two weeks and waiting and hoping it hardens.
for the record, I have learned to always prime first (Rustoleum gray primer) and then, as poniaj says, to do light coats.
