Most of the time it is OK to do this -BUT at a low overall temperature with plenty of ventilation. If you know what you are doing, this can result in a better overall paint job. The problems with this approach are solvent pop, wherein the solvent in the paint is literally boiled to the surface (not quite exactly like solvent pop in car paint jobs - thats when there is too much solvent in the paint to begin with) you'll see a good tendency toward self leveling but the paint on the whole will tend to shrink. And of course there is the tendency to actually heat the solvent up in combination with increasing the concentration of the gases (closing the oven door) - creating a BIG bang in your week. Most paint professionals that want to speed the drying time/harden the surface/etc use infrared lamps. The lamps will heat the part, not the air around it. Consequently, the air can be circulated - and no big bang. SO, if you're going to do this use some common sense - or something resembling what ought to be common sense.