(big snip)

Prestec products,
For my mostly wood SHK, After sanding CAREFULLY down to bare wood (discovering original pencil marks!) Prepped bare wood with 3 coats EV-400 epoxy varnish, then Prestec 2081 white epoxy primer/filler, "block" sand with 5 foot long fiberglass sanding block, also used 18 inch long sanding board and various smaller hand pads, final sanding primer/filler with wet 400 3M then used randolph ranthane.
Prestec 2081 primer/filler is marketed for Wood or composite surfaces (radomes) sombody with a glass ship would pick another prestec product maybe?
For pinhole filling I also used activated "Auto body" products at first, However Prestec supplied me with their White epoxy filler product, Less viscous, more liquid, and after a short learning curve, Much superior to car products.
BTW, when using air tools, be judicious with the air tool oil, I sometimes wrapped a shop rag around the tools exhaust to minimize oil spray on my surfaces. also meticulous intercoating surface cleaning ensured good adhesion.
P.S. the 5 foot long sanding block was a section of fiberglass U channel used to make ladders. A local buddy is an aerodynamacist at a wind generator company and supplied me with it, they use them for mounting electrical components.
Good Luck!
Scott W.