Two things to consider in refinishing are 1. What is the original finish and 2.
How deep is the graffiti and how much is there? If it is deep and there is a
lot the planer seems like the way to go. If this is impossible you could rent
a belt sander intended for floors. These will really cut so be careful or
you will get deep gouges and an uneven surface! For more minor Stripping hand
belt sanders will work and you can get them with a vacuum attached to minimize
the dust problem. Sanding Epoxy is bad news so if your original finish is Ep
oxy the planer looks good again. Personally, unless you do a lot of wet stuff
I'd suggest an oil finish instead of urethane or epoxy. I think you will find
it easier to apply, it will look nice longer, and will be easier to repair or
refirbish when it becomes necessary again.