[Kunama]

Love the tube you made !!
Not a fan of waterbased PU varnishes.
I use oil based PU as they give a better, harder finish and with proper sanding between coats, they give a very much smoother surface.

Edit:
Clear Cabothane is easy to come by and does well, a quality brush should be used, don't overwork the stuff (once it is brushed on fairly evenly don't go back over it if it has had even a minute to cure)
sand between coats, 3 coats will give you a really nice finish