Hello, I want to seal my jnats. Went to home depot and was looking at clear polyurethane. Its got oil in it . There are a few types, thompsns watersealer for masonry, water based oil based etc. Any advise as to what to buy. can I use a spray if I tape the top surface of the stone, wash each stone and let dry for how long,and how many coats and how long before I get it wet after sealing. And any other advice as Ive never done this before. Im asking alot here fellas I know, but I dont want to mess it up. I dont think an air gun is agood idea, or is it? Thanks