Gary, yes I spray all my dope with the Preval units as I build slow and don't need to have a big spray gun to clean. The thing I like about using the Preval system is you get the simplicity of a rattle can with the ability to adjust the mix and can add retarder (if needed), then just toss the whole thing (I do save the jars). I usually start around 40/60 thinner to paint and here in FL add 4-5% retarder. I like the Brodak (Randolph) thinner as it gasses off in a few days. The tip blow back trick is something that I recently found out about from the Preval web site. I had several units that would spray water but when paint went it sprayed for a bit then stopped. The blow back cleared the problem. I think I should strain the paint before putting it in the jar and keep the pickup tube screen in place for use that should eliminate the problem but if it stops the blow back can clear it.
Another tip is to have a jar with thinner (cheap hardware store lacquer thinner works for this), once you are done for the day, take the power head wipe down the excess and spray thinner through it to clean. Keep the power head on the thinner jar, when ready to use. say the next day, give it a quick spray of thinner (might do a quick back blow) then go to the paint jar.
Best, DennisT