Spray-on paint hardener for enamel?

Is there such a thing as a hardener that can be used on enamel after it's been applied, even if it's already cured partially? I'm looking for something similar to spray-on activator for super glue.

I want something that can make enamel hard enough to be sanded without the usual long wait, and neither heat nor lacquer are options. I realize that there are two-part paints that will harden in less than a few hours, but I'm looking for something different.

Even gentle heat accellerates most reactions.

Heating even to 50 or 70C in an oven, or with a heater means that it'll dry lots faster, and most things can take it, apart from waxes and animals.

Why is heat not an option?, What are you painting? and what paint material are you using that you are calling an enamel?, An enamel is just a posh name for a hard glossy paint.

You can add accelerators or reducers to synthetic, alkyd or polyurethane paints, Terebine for example on these paits will speed up the drying process by several hours but the inner surface will always take longer to dry anyway with air drying synthetics as opposed to chemical curing twin packs.

What's wrong with heat?

Priceless 16th century cheese and styrofoam sculptures. Actually plastic, like styrene and PVC, which can start warping even in the trunk of a white car in the summer.

The oil-based stuff from spray cans that's not lacquer, epoxy, or latex.

I thought that maybe there was something that could start a catalyst reaction that would penetrate all the way through.

It'll melt what I want to paint.