What is the best means for removing a modern polyurethane finish?
Use a good quality paint-and-varnish remover and lots of it. Polyurethanes have a way of soaking up stripper, so don’t start scrubbing it down with medium steel wool until it is loosened all the way to the wood. After the first coat is absorbed, apply another. It is a bit more costly, but otherwise you end up with part of the finish still on the wood when you start sanding.
