Honestly, as an old school melee veteran that is very much enjoying Ultimate right now, I will say that I'm having to actively fight against my melee muscle memory. It doesn't help that my melee main and Ultimate main is M2, which has DJC and other weird tech that doesn't transfer over.
That said some things might be at least a little bit worth doing, in a general sense. Here is some stuff to practice:
Quick turnaround jabs, and tilts (tilting in the opposite direction enough just to turn)
Dash dancing (it is different in Ultimate, although M2 so far feels the most melee of those I have played)
Short hopping
Fast falling
Teching (the windows seem a bit harder to hit in Ultimate than in melee, although I don't have frame data)
Short hop reverse B moves (like doing turn around lasers with falco, fox, or turn around shadow ball with M2)
From my experience so far with Ultimate, subtlety is the name of the game. You want to have really good accuracy with your movement, and that is being able to have really precise movements with your control stick. I hope this helps!
