Penetrating epoxy is great to use for a finish, only problem is it has no UV protection.
I think Phils post about not using penetrating epoxy was for actually gluing up stocks not finishing them.
Most products say to apply the first coat thinned.
This is what I have used on the guns I have just finished making.
8 coats of everdure (evedure is a penetrating epoxy available in australia, not sure if you can get it in the US). It is very thin and easy to apply with a glossy finish.
4-5 coats of marine varnish. this is high gloss but dulls when sanded, can be buffed back to gloss but takes to long to sand with 600 and then 1200 then 1600
the fina 2l coats is penetrating epoxy.
the penetrating epoxy does yellow but takes along time as all the under layers are protected by the varnish.
When the top layer scratches I sand it back to the varnish and wipe another coat of penetrating epoxy over.
soon enough I will find away to gloss the marine varnish and then I can do away with the top coats.
To stop the epoxy and varnish going off between coats I put it in the freezer