For walnut you can use bees wax or get an oiling kit from your local gun shop or go to a good wood yard that supplies wood and oil for the furniture hobbyist/trade. I'm just about to try a "Trade secret" oil kit.
Many years ago when I was a boat builder I knew a boat builder called Jack Chippendale, he was some thing like great great great great grandson of the master furnature making Chippendale(not the male strippers). When varnishing boats he started off with 75% thinners to 25% varnish, then 50/50 then 25/75 and finishing with about 10 to 12 coats of varnish. The wood looked like it was under a sheet of glass, it was the best wood finish I've ever seen.