My uncle insisted I use a 4-inch foam brush for a shellac job on a 1920s sideboard, and the finish came out perfectly smooth. | Furniture Finishers - Opinions Matter
Your uncle was totally right about the foam brush. I tried using a cheap bristle brush on a similar project and it left tiny lines everywhere, like you said. The foam just lays the shellac down so flat. It's one of those things that seems too simple to work until you try it. I keep a pack of those foam brushes just for shellac and wiping on poly now.