After 6 months of tinkering...

Blows powder thru the front barrel, using a NOS solenoid, high pressure lines and a servo operated cam to trigger the micro-switch. Pressure tank is buried in the center section, and is constructed from two thermos bottle inner liners welded together. Holds 300 psi easily. Filled from a paint ball Co2 bottle.

I am currently using flour as powder, but need some suggestions for a dark colored substance. I've thought about black pepper...but that could lead to a sneezing problem.