YESSS
OK HERE'S HOW YOU DO IT. SCREW ALL THOSE VIDEOS OF PEOPLE DOING IT EFFORTLESSLY, OR PEOPLE TALKING ABOUT WISDOM FORM BECAUSE WISDOM IS CRAP AT THIS.
- Equip Fatal Crest on Sora, and Sleeping Lion for Master Form. Equip two Form Boosts.
- Go into Master Form.
- Cast Curaga and wait until the MP recharge bar is under the O in FORM.
- Start the duel, start mashing the attack button like crazy.
- ALWAYS TILT THE LEFT ANALOG STICK IN THE DIRECTION THAT THE MUSHROOM IS FACING. This is important so Sora is always facing the direction that the Mushroom eventually goes flying in (and trust me, it will fly away many times).
- When your MP is recharged, get ready to spam Thundaga. Make sure you're UNDER the Mushroom when you start spamming it, and hope that it or you don't get stuck on a corner of the map and can't move.
That should net you over 85 hits. This bastard took me over 4 hours in total to do and I'm actually a bit sad I didn't get 99 hits.