How about just water?
If you are looking just to get the dust off, a weak soapy solution with a light scrub/mop followed by a rinse should suffice. Why use acetone?
Acetone shouldn't turn gelcoat into mush if you just use it to wipe it down. Acetone is very volatile, it really won't sit on the surface for more than a few seconds in any time of temperature or breeze.