I use epoxy resin but I hit it with a heat gun to get it to be thin and runny, then paint it on and squeegee it off. It fills pin holes and any exposed weave and any dry micro porosity. Shine a light at a very low angle to the surface to expose voids, pin holes and other irregularities. Lighting is critical to good surface prep and painting.
You can also use a high build primer and rub it in with your fingers, but I like the epoxy method. It is a one stop sealing procedure for everything.
Old school simple VFR RV 4, O-320, wood prop, MGL iEfis Lite
VAF dues 2019