Luigi HIGHLY specializes in juggle traps. It's matter of reading your oppenent's DI and being a step forward. Most of the time, i read or bait the airdodge and just pretty much after that. The options he can pull off are :
Pivot grabbing ( works highly well espically when you can mindgame and read well) also resets the situation if you dthrow them
Sliding pivot up angled fsmash ( perfect for surprises and punishing)
reverse upsmash ( you can charge it if you read a airdodge as well)
rising nair ( comes out instant frame 3 and lasts up to 31 frames, lasts longer then airdodges, perfect for punishing airdodges and resetting the situation )
double Fair/thirple fair ( lol funny for walls )
Bair/double bair/Buffered bair ( same as above ^^, but in general overall better )
jab upb / upb ( again, powershield to upb is too good)
PS OOS Upb ( perfect for ppl who love to use aerials as they hit the ground like marios Nair.)
airchase tornado/ground chasing tornado ( lasts long, perfect to cover air and ground )
Upair binds ( good after baiting a aerial atk or airdodge)
OOS pivot grab ( extremely good who love to space their aerials)