Making plastic look like plastic

It seems like 90% of this hobby is about making materials appear to be something they're not. Most of the time, it's plastic into various metals.

I'm looking for tips and tricks to make plastic kit parts look more "plastic-y," in particular white plastic. The best examples I can think of are common plastic radiator fans, and that milky-white translucent plastic that gets used for under-hood reservoirs for various liquids.

Discuss. Please and thank you. :)

The best idea I've had, and I think I've seen, for the radiator bottles, is prime it white, paint half "fluid color", then paint the bottle white again with a thin suspension of white paint, ie 1:5 or something white to flat base or something like that. I've seen some folks here make those parts out of clear, and do something like that, I think, but without the white priming.

For the radiator fan, I dunno. Perhaps paint if flat white, then kind of polish it, or wax it, to give it that sheen but filmy transluscency.

What I do is paint the part flat white (or whatever color you want, but flat) and then, after it dries, take your fingers, rub it on your forehead (yeah I know kinda gross, but works great) and then rub those fingers on the part. The oils in your skin makes the paint sheen, like a plastic part. Very old trick they used to use on leather upholstery back about 10 years ago - makes for a good vynil sheen ont he seats as well.

guy who paint little lead figures would paint the effect of the translucent white plastic who coloured liquid contents.

this involves painting-in the liquid and applying a dark-line and highlight to the liquid part of the (let's say bottle) and then when this is dry, apply a watered down/thinned layer of a flat white.

have a look at how warhammer 40K guys paint their translucent containers.

i know this isn't really idea foe how model cars are normally done but i can't think of how else to simulare translucent plastic without actually scratching a translucent part.

Just like slk320 said, I just rub it with the oil from my skin. Works great.