Water based clear protective finish coarse first coat
As implied by @keshlam in his comment, you should do some reading about finishing wood floors with waterborne finishes.


waterborne finishes are typically applied in several thick coats, it is especially important on woods that are prone to raised grain; the thick coats will bury the raised grain.
for large areas, water based varnish is most often applied with synthetic applicator pads, working quickly to maintain a wet edge. A brush is used along edges and in corners.
required large area sanding between coats is often accomplished using a stand-up random-orbit vibrating sander specifically designed for use on flooring. Supplemented by use of a hand-held sander along edges and corners.


You should visit a good paint shop near you, much advice can be had. Often these shops rent the equipment needed as well.