The best way to strip the finish off of wood is to use chemicals, don't even think about trying to sand it off. I get half done projects in my shop all the time, most of which people have sanded like crazy and then given up when the going gets tough. This is not the way to get the job done effectively, it costs so much more in wasted sandpaper, skin from your fingers, and mountains of patience, plus it doesn't get the finish out of the grain of the wood
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So what is the answer.... well ..chemical stripper... Brush some of that stuff on almost any finish and it will take it off in a matter of minutes. The trick is to let the stripper do most of the work, letting it soak in, so it can eat away while slowly sinking deeper and closer to bare wood. Then it must be naturalized with some kind of solvent or what I like to use, lots of hot water and a scrubbing brush.
As you can see with this dresser it stripped really well, almost all of the finish residue is out of the grain ready for a nice even coat of stain.