If you know all of ness' tricks i can't help you out in that aspect, but:
For ness, Uthrow > DJC Uair in great for DI in, if the opponent DI's out Uthrow > DJ > Bair. On floaties don't DJC, but on fast-fallers DJC would work to extend the combo.
If the opponent is caught in the PK Fire, DJC Uair is really good for racking %, and the best move to hit with after the PK fire has ended is usually Uair or Bair.
Some basic stuff i know, but i have on my channel some of the best ness dittos i've played against Nstinct, one of the best Ness players to play ssf2.
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" You know what neither Melee nor Brawl have ? Controller input history in training mode." - 228zip, 2013