Things You'll Need
Medium and fine grit sandpaper
Foam paintbrushes will work with almost any paint or polyurethane on any project. They are cheap enough to toss away, although they can be cleaned and reused several times. They hold the liquid without drips making them user friendly. Compare the price of foam and bristle brushes and you will be happily surprised.
Purchase the correct size of paintbrush. Foam brushes come in 1, 2 and 3 inch widths. They have a beveled end for cut-in work and a wooden handle.
Prepare a can of polyurethane by stirring it so it is smooth. Prepare the surface of the project by sanding and wiping with a tack cloth to remove dust and grit.
Dip the foam paintbrush into the polyurethane. Fill it only half way up. Overloading will cause drips. Begin painting the surface with long, smooth strokes. When the polyurethane is almost out of the brush, lift the tip to a 45-degree angle and pull off the board so that there are no lines.
Continue until the project is completed. Either dispose of the brush or if you desire, wash the brush under cold water. Squeeze the polyurethane from the foam until the water runs clear. Dry and use another day.
As inexpensive as foam brushes are, you can actually make your own with a tongue depressor, household glue and a piece of foam shaped into a brush.
Foam paintbrushes are not appropriate for shellac or lacquer because both products dissolve the foam after a short use.