I discovered I have an external mix brush. It was part of a package where I got a compressor and 3 airbrushes. I didn't know what it was for or how to use it until I read this column and saw the suggestion to use it for resolene.
Sure enough, 30 seconds after I started using it, it was clogged. Aaaarrrrrggg! I back flushed it by holding my finger over the tip. Lots of nasty semi-hard stuff was flushed back into the bottle. After a few times, it was working again. Now this is a really cheap piece of c*#p. I guess it is only $10 tops. I found I could regulate the flow. At lower flows, it didn't spray. At the lowest setting it would spray, it was too strong. I was able to do it only by spraying bursts. I'll continue you playing with it. If I get it to work right, perhaps I'll report. I was really excited to think I could use the air brush to spray resolene. hmmm.