Oswalds65Chevy,
I haven't done the brush deal, but have some thoughts on it. It would seem to me that any true automotive primer would be too 'fast' to paint with a brush and not leave heavy brush marks.
If it were along the lines of a RustOleum primer, which might be reduced with mineral spirits and give time to flow and level, then it wouldn't be the proper base for any automotive paint applied over it.
There are lots of things floating around in the realm of auto paints, tractor/implement paints etc...so this might be a do-able thing. Keep us posted and good luck!
Stuart
