I have been skim coating my filler with the metal glaze and have noticed a few tinny tinny pinholes in it. I this anything to worry about or will the K-38 high build fill them? :confused:

A good urethane primer "can" fill some small pin holes, but you should have none.

You need to not "whip" up the putty when you mix it, fold the hardener into it applying pressure to press the hardener thru the putty.
Then when applying it, again use pressure to thin it out and press all the air out.

The only time I get pin holes in polyester putty is when I am asking it to do something it isn't designed to do. When I am asking it to fill more than I should, that is when I get pin holes.
If it is a thin skim coat, I will never I mean NEVER get pin holes.

I was probably spreading it on to thick. Thanks Martin. I am using the metal glaze that comes in a tube. Am I getting air in it by squeezing it out of the cap? The hole is only like 3/8in. should I take the cap off?
Pressing it is tough, because it runs all over the board, should I just keep scraping it back into a pile and pressing again? I find that wiping the spreader on the edge of the board is the only thing that saves me