I only use a siphon brush for clear coating, cleaning involve spraying acetone through the brush 3 times, then disassemble and drop the needle, nozzle, air cap etc into a jar of acetone to soak. The body of the brush gets cleaned out thoroughly with pipe cleaner soaked in acetone.
As far as clear coat, I spray Tamco 9500HC automotive urethane. it is a far superior finish to any epoxy I ever used in the past. Rock hard, ultra clear, doesn't yellow, is actually rated for submersion unlike many epoxies commonly used, and it can be sprayed on swimbait joints with no effect on action. It is also ultra fast, hooks and hardware can be put on 15-30 minutes after the final coat. I can line up 30 baits, spray 3 coats and be putting on hardware and packaging in 1-1 1/2 hours (cure time can vary with shop temp).
The downsides; it is highly toxic and requires both excellent ventilation and a respirator and clean up is a slight pain. Also, it doesn't spray well with a gravity brush, I use a Passche VL with a 1.08 nozzle. a .68 nozzle can be used if you reduce it.