: . . . currently "fair" spots where the fibreglass weave still shows
: through I'm wondering will the 6 coats of varnish take care of it (ie.
: make it totally smooth in the end)?

Don't rely on the varnish to do any filling. I don't know why you are putting on 6 coats, but the varnish is quite thin compared to epoxy, so multiple thin coats would eventually build up to something in the valleys of the fabric weave -- but why? You would only be spending your time on sanding off the varnish that was sitting on the higher spots.

On the other hand, thick coats of varnish would fill those valeys faster, but they would take a longer time to harden, and you would be more likely to have runs.

In either event, using varnish as a fabric filler is a time consuming proposition.

A light sanding of the fiberglass between applications of resin does a nice job of removing the excess amount of resin that is on the surface of the glass cloth, knocking off the plastic peaks, and giving you a beter chance of filling in the remaining valleys with fewer coats of resin. The idea is to do this with a light touch so you don't go through the resin coating and hit the underlying glass fabric.

Most people prefer to put on two or more coats of resin, ensuring a thicker coat of plastic over the glass fabric, before they do any sanding, but I suspect that a few minutes of hand sanding, with something no more complicated than a sheet of fine grit sandpaper wrapped around a block of scrap wood, would go a long way toward a great finish, and a lighter boat. Just go over the entire hull, applying about as much (or as little) pressure to the sanding block as you would apply to a sponge when washing your car. After this rough caress, remove the dust and put on your next coat of resin.

hope this helps

PGJ