Hi Arthur,
I ran into the same thing with the tiny bubbles when I put the second layer on the football area of my guillemot several days ago. Just in a couple of places though. Still haven't found the cause. I am also a first timer and using foam rollers.
Be carefull when sanding, I went too deep in some places and it does show up even after more fill coats as a sort of hairy look.
Next boat I will put on a complete second layer instead of just the football.
The best way I found to fair the transition of the layers was with a carbide scraper.
Richard.