Tom,
I'm working up an idea for coating moulds with a dry mould-release.
There are lots of drafts and returns in the mould formers that would allow only a fairly long-bristled brush to reach all the crannies -- a buff or rag won't do. The brush bristles should be about 2" long, and fairly stiff, so the stuff can be "scrubbed" onto the surfaces. They'll get deformed a lot, so should have good memory, and not break easily.
The bristles also need to be flagged a little to hold the dry powder.
A densly packed brush like a manual scrub brush would be the best format; 'bout 2-1/2" x 6" style?
Does such exist?
LLoyd