I *highly* recommend the stop-loss bags from CLC. https://www.clcboats.com/shop/products/boat-building-supplies-epoxy-fiberglass-plywood/marine-paint-varnish/clc-stoploss-kit.html
As far as pin-holes go – it sounds like you’re describing fish-eyes. These are caused by some sort of contamination on the surface of your project. I’ve heard a number of things will contaminate the varnish, so it’s best to avoid it altogether.
Anecdotally, I’ve heard the following things are known to cause fish-eyes:
- Any kind of oil mist in the project area, lawnmowers, air fresheners, candles, etc.
- Pollen, localized grass-cutting, etc.
- Fabric softeners and/or dryer sheets, especially when used on wipe-down rags.
- Some covers may have PVC out-gassing issues.
- Contamination from fingers, hands, etc. (Ooo, it looks like glass! Is it wet? Lemme touch it!)
You get the idea… TRUST NOTHING.
What can you do about it? Vigorously scuffing (matte finish) the most egregious violations. Followed by:
- A wipe-down with denatured alcohol, using a clean cotton t-shirt material rag.
- A wipe-down with blue windex, using another clean cotton t-shirt material rag. (ONLY BLUE WINDEX.)
- A wipe-down with denatured alcohol, using a third clean cotton t-shirt material rag.
And waste very little time after you’ve completed the three wipe-downs.
I was successfully able to launder my t-shirt rags using unscented dye-free liquid laundry detergent, and a healthy dose of bleach. And remember, don’t use laundry sheets in the dryer!
Good luck!