It sounds like you're there. The dull indicates the high spots and the shiny the low. If you are sanding over the glass fabric you don't want to sand into the fabric because it will weaken the area and the weave will show through. Sanding could fill a book and it has accounted for many posts in this forum. If you don a search on sanding on this forum I think you will plenty to read.

Thanks Catboater  - 

I did a search and didn't find what I was looking for,  I will try just the word "sanding."   No fabric here - just epoxy over plywood.  

One of the things I think I am doing now is learning how to work with epoxy,  I figure I'll build skills as the project moves along.  

John

John,

The trick is to stop sanding and put on another very thin layer of epoxy. That will fill the speckles and then you can give it another sanding to get it totally uniform.

That said, if the speckles really are tiny, the finish will take care of those. 5 coats of varnish will certainly fill them, as will the multiple coats of primer and paint if you're going that way.

If you do sand through to the wood it's no tragedy. Another thin coat of epoxy will fix that just fine. It's glassed surfaces where it's more critical.

Have fun,

Laszlo