Is there such a thing as using a old spray gun to apply thin
layers of bondo...Can bondo be thinned out and sprayed..


Sprayable fillers (i.e. bondo) are a different product. Their technical term is polyester primers. The brand names are Evercoat Featherfill and Marhyde Quicksand. Here is a link for the Marhyde:
http://www.smartshoppersinc.com/closeouts/MarHyde-Clearance.HTML

Regards,
Steve
New Orleans