Lots of the skin on frame kayak guys use polyester skins (heavier
weight than airplane however). They prefer oil based house paint, and
just thin the first few coats enough so as to have it soak thru the
fabric to encapsulate the fibers. Just a data point from a similar
construction style. Never tried it on a plane.

Brian Huffaker, DSWL )
RV-8A #80091 countersinking cockpit rails
Starduster Too 23UT flying