Guys,
Found one thing that makes the Preval Spray System work reliably is to strain the paint. This is very important with any spray system but doing it for the Preval is something that eliminates the plugging that some have experienced. The Preval bottle has a smallish neck, I tried using a gauze pad over the opening, making a pocket and pouring through. This worked but was very slow and a little messy.
I found that using a simple plastic soda cut a few inches from the open end, sand off the molded in threads and it fits nicely into the Preval bottle neck. I use a section of Gauze pad inside the funnel. It is easy to pour a good amount into the funnel and filter it without it going all over.
Best, DennisT