Huh... Lou is
OBVIOUSLY some kinda anti-enamel hate monger!
To elaborate just a bit, yes, they will stick to plastics since that's what they're made for. It's pretty much the same rules as for acrylics in that they don't stick well to polyethylene but stick fine to polystyrene and ABS. They DON'T work on soft vinyl and are very likely to stay tacky forever on those surfaces.
They thin and clean with oil based solvents, just like artist oil paints. Probably best to go with some sort of odorless and/or turpentine substitute to avoid a contact buzz. (Then again....)
You might be able to use them over chrome (vacuum metalized plastic) and in fact, they might even adhere better than acrylics. Without trying it on that specific figure, there's no way to know for sure, although a slippery, shiny surface is probably going to be a pain whatever paint you use.
They usually do take longer to dry than acrylics but like Lou said, it depends on all kinds of factors like temperature, humidity, the surface it's painted over, etc. Just like with acrylics, whether they dry glossy or flat depends on whether they're made to dry glossy or flat. It should tell you on the label which type it is. I find flats MUCH easier to paint with, especially if you're using a brush.