There's two different problems that might be present, pin holes vs.
cratering.

Pin holes in an epoxy coating are caused by air bubbling out of the wood.
As the epoxy cures, it gets warm, the air expands, and out it comes. The
trick is to prewarm the surface, either with the hot sun or with a hot air
gun. (I use a Black and Decker paint stripper type.) That way the surface
is cooling and the epoxy is drawn into the hole.

Cratering is tougher. It's a failure to bond. Surface tension pulls the
epoxy back away from the spot. I've seen suggestions that one should scrub
the epoxy into the surface with the heel of the roller or maybe "wet sand"
the liquid epoxy into the surface. (Messy!)

Roger

http://home.earthlink.net/~derbyrm

"1088" wrote in message
...
Still fixing my fixer-upper. I chiseled and sanded the crazing in the
gelcoat, then filled with several different things and the cracks are
covered ok but the tiny, tiny pin-holes will not fill. Many of these
looked like tiny black spots at first. Any attempt to fill them
results in some kind of gassing and the filler just ozzes back out
after a while.