re: polyurethane application

Well i went to home depot and bought another brush, this one says its for poly applications. I am hopeful, looks better, i will be sanding with steel wool (0000) and soapy water. I do not want to strip the table and start it over so i figured i would give it one last shot.

Question about thinning, with oil based poly, you thin it with mineral spirits, with water based poly, would you thin it with water?