dunno about brush applications, but I have run it through one of my old hvlp sprayers. huge tip no filter. worked fine, but cleaning the machine was a pita. I would guess a 1/2" nap roller pad would be best

 

I have used body Schultz (spelling?) In the past it is bought at a place that sells to body shops sprays from a special gun, I currently use flex seal it seems OK for now used it and metal tape to seal up the holes in rear arch an firewall and seal up the hvac intake trough

I have a poor opinion of por15 my brother did his lifted zr2 frame, followed all directions, bought everything the directions said in their brand, 2 years later the frame is rusted worse then in the beginning and he only drives it in the winter and never off road, looks like the por15 made the rust worse like rust under powder coat, ymmv

 

Take a look at Eastwood's rubberized rust encapsulater

http://www.eastwood.com/ew-rubberize...ero-15-oz.html

I am considering using this on my DII frame.