I managed to score some purple heart out of the local wood recycler which, after a lot of work, is now coming together as a bookcase. I didn't have quite enough, so the back panels are veneered MDF on which I have had to use a stain to bring in line with the rest of the wood. I've also applied a (very much) watered down stain to bring all the wood to a similar appearance. This now looks great (despite my reservations about the stain) and I really don't want to wreck it by slopping on the wrong finish. The stain is water based and is also watered down. Any suggestions on the varnish / lacquer / any other front. While the wood is (very) hard wearing, I would still like a tough finish.