> After my final sanding of the last epoxy coat, I sanded into some of the
> glass cloth which is obviously white. Question, can I now start varnishing
> or must I apply more epoxy first? Thankyou for your help!

You should be able to start varnishing. Wipe down the boat with a damp cloth. You should not be able to see the white while it is wet. If you cannot see it when the boat is wet, you will not be able to see it when it is varnished.

I had a lot of that white showing on my boat prior to varnishing. I put on the varnish, and the white disappeared.