Thompsons sux, serious, nothing but paraffin wax. yes it's a sealer..............you can seal wood, or feed it oil as it dries.
I feed my hardwood deck, not seal it.
that said, get a stain stripper, spray it on with a pump wand garden sprayer, wait 10-15 minutes.
pressure wash clean
this is YOUR FRIEND!!!!!!!!!!!!!!!!!!!
awesome rotary large surface pressure washer attachment, I'll never use a wand again for large surfaces.
Shop Briggs & Stratton Rotating Surface Cleaner at Lowes.com