Any idea of a method to clean the insides of a light housing?

Anybody have any ideas how to clean the inside of the turn signal (front or rear) housings on a 95 Cherokee? Basically I'd like to clean the reflector surface and make it shiny (kind of dusty)

Only problem is, I can't reach inside!

I was figuring I could fill the housing with some sort of liquid.....but what liquid would work best do you assume?

Thanks!

Do you have the housings removed? If so, use soapy water with a paper towel inside, and shake it. Then fish the towel out, rinse and air dry. Don't use any solvents that may harm the plastic.