: while I was doing 150 grit sanding, I noticed some small pits in the epoxy.
: pin head size. Will the several coats of varnish fill these in?

Eventually. You can fill a lot of stuff with a thick coat of varnish, but you risk it running. the varnish is made by dissolving a resin in a solvent. As it dries the solvent evaporates -- slowly. The surface, having the greatest exposure to the air, starts to harden first, trapping the solvent in the varnish that is underneath it. The thicker the coat of varnish the longer it takes for that buried solvent to eventually evaporate. Until then, the varnish is a jelly-like glob that you can't sand or work with.

So, we put on very thin layers of varnish, allowing the solvents to evaporate rapidly. and we build p the arnish protection with many thin coats.

With pits, you'll easily fill them with varnish, which will shrink a bit as the solvents eventually evaporate. A very light sanding will blend he endges around the pit into the varnish and give a nice finish. Eventually. Unless you wait until it is solid, the varnish in those pits will get pulled out as you sand, making a mess.

PGJ