It's finding those openings that is tough. But I guess it's all patience, one of my weaknesses...
The specific openings will change depending on who you play, but I guess some are pretty universal.
I've been Hbox's falco guinea pig for the last 2 months, he really doesn't leave many openings but when he does its usually
a missed L-cancel or early Dair, this gives you a chance for a shieldgrab, but its hard to spot.
he drops from platform or bum rushes with a dair/nair, I like to wavedash back as he approaches, but not a full wavedash, so as soon as he misses I can dsmash or grab.
Zoning/spacing with dair is really good.
U-air when he dairs into platforms, this can lead to some follow ups, but most of the time it just tacks on damage.
Timing Usmash for invincible head is apparently really good but I haven't really gotten the timing down.
Techchasing is really important in this matchup, once you get the upper hand you really have to milk it since Luigi is awful in the neutral game against falco.
Unfortunately, the shine comes out super fast, so what looks like an opening sometimes just results in a shine to the face.