Turpentine, acetone, goo gone will all eat the plastic your going to be stuck with media blasting it with something softer than it or you could try heat and rubbing alcohol but be very careful with the heat most plastics melt before paint does...
Supposedly you can do this with an airbrush i know they sell cheap plastic beginner ones that run off a can of air... at stores like hobby lobby... alternately http://www.chicagoairbrushsupply.com/bamo260spgun.html not that expensive this plus a box of baking soda.