Getting a smooth, blemish-free finish with oil-based polyurethane is within your grasp if you follow the steps in this article. Oil-based polyurethane varnish brings out the wood’s natural beauty or wood grain. Our 4-step approach shows you how to apply the varnish successfully. A good-quality natural-bristle brush, a reasonably dust-free, well ventilated space and some patience are all you need. Learn how to apply polyurethane.