From looking at the pics it really is hard to see the problem. I am going to throw some semi-educated guesses at you.
Anything on the piece, dust, will be there when you paint the primer or sealer. You will have to sand these pieces back to metal to be rid of them.
What is the cure time on your sealer? Is it a primer sealer or a color sealer. I am not familiar with the product as far as numbers go.
IMO, it sounds like you're not putting enough product on, it is coming out dry and feeling rough. If you can see marks from the tack cloth, it is probably not enough material laid on the parts or a cheapo tack cloth (harbor freight?) that shouldn't be used for car painting. Over-spray is more evident when you paint a piece, it drys, you paint another piece and the over spray settles on the dry piece. I don't think that is the problem. If nothing else, get the slowest reducer available.
If you're using a sealer type of paint, one that goes on before the color, the primer must be baby butt smooth. The sealer must be done as smoothly as your paint. The sealer may not look as good as paint, maybe try doing a small piece where everything is as should be and seeing the results. The piece won't look great until the clear is applied. Good luck.
I looked over your pics again, I am thinking this is too dry and your pattern (from the painted test on the wall) needs adjustment. That's a very narrow pattern and will not help you get a wet coat.
"When I was younger, I could remember anything, whether it had happened or not." - Mark Twain
Last edited by dinger; 05-09-2012 at 12:47 PM.