Hey Youie,
Your first good move was the airbrush. The Faskolor paints are great for lexan, although you may have to thin them slightly to get good flow out through your airbrush, the thinner the paint, the smoother the fades, but the thinner you'll have to apply it, for solid colours it can be used straight. As far as backing a candy goes, typically you would use a metallic like silver or gold to tint the candy. Flip paint is a colour shift paint you typically back with black for maximum results, candys are not the same as flip or colour shift paints. You can also use chrome backers like Alclad or Spaz Stix to back your candy, just remember to back your chrome paint with black. Because the Faskolor paints are water based you'll have to work more slowly than spray cans, you might want to get a hair dryer to dry the in between coats more rapidly. For free paint mask templates feel free to visit my site
www.rcinfusion.com and go to the 'Free Things' section.
Hope this helps.
Rob