The early/late thing probably depends on what move hit you, at what percent.My DI must seriously SUCK. I've tried this again but I seem to only live like 2 or 3% better than if I had used a DJ.
I think I'm definitely mistiming when I can bair from knockback - how can one tell when they need to bair? There are times I can do very early, and other times when I can't do it at all.
To get that bair out ASAP, just mash the C-stick after you've been hit. DI is only when you're actually getting hit. So mashing that C-stick will only affect your DI if you mash it while being attacked - if you do it while you're flying, it has no bad effects.