Way back in the middle of August, two months ago now, I epoxy-coated a piece of wood using peel-ply to ensure that no amine blush remained on the surface of the epoxy and that it was ready to be coated with varnish. Since that time I have added more coats of varnish, about ten in all.
Here is the result. Not a bad finish all told.
Another view and although there is a little moisture on the surface due to the temperature and humidity, you can just about see that the surface of the varnish is fairly good.
The bad news is that it took over a month for the first coat to harden to a point where it was not tacky to the touch. Subsequent coats went on normally, but that first one took an age to go off and that was in a warm environment.
So the conclusion of this little experiment is that sellers of the varnish are correct when they say that they do not recommend using Le Tonkinoise varnish over West System Epoxy. You can do it, but it is not a straightforward task.