Bob,
I've been using the Paasche VL dual action brush. It is quite the workhorse. I have three brushes, with three different tips that I use almost daily. In the shop I use a hobby compressor with no regulator. I'm guessing that it is putting out around 25/30psi. Most of the floquil RR colors in flat finish flow just fine without being reduced. The gloss colors need a small (up to 10%) amount of thinner. Thinning the clears (Dullcote and High Gloss) will help to reduce orange peel and give a better flow out.
Dave