Using a sander to remove paint is time consuming and messy with all the dust.
A grinder will remove the paint much quicker, but again the dust.
Either way you need to wear a dust mask.
I would recommend a chemical paint remover to soften the paint and scrape off into a pail. Then you can sand or use a grinder to cut the last down. Then you can use a long board to find the highs and lows to bodywork into shape. This produces way less dust. Whether paint, body filler, abrasives or steel removed, you produce dust doing body work. The less dust the better.