I posted them a while ago in detail, might be worth looking up but the gist of it is:
KK's guide to being gay to skating clowns:
My credentials are ****** Vudujin and Abate at HOPE something with this strat (as Fox or Sheik) and doing almost nothing else, you can dispute if you want but it's IMO and it's been effective vs all Luigis I've played after that (although I've not played Eddy or Ka)
Anyway, let's begin
Basically stay outside his f-tilt and d-smash but still inside his medium WD length
Punish his flailing because he now can't defend on reaction or space without retreat WDing to try and redo the whole situation (Luigi's got limited movement options so prey on this - even if he's fast you're just as fast and more maneuverable which is a big advantage)
Press him to the edge when he WDs back and force him offstage (if he can't ledgedash with invuln then you win at this point by bair/shine/grab suite)
When gimping him in general, remember he has low stun & fast aerials so be vigilant for DJ fair recoveries and block > shine them (he has other stuff but DJ attack is the most important to watch for 'cuz it's common and you lose your advantage if he gets it - other options can be managed after the fact most of the time)
Stuff WD approaches with u-tilt or hard aerials (nair, bair) to prevent CC - you can also grab and toss him onto a plat, above, or towards the edge (whichever makes most sense)
He has poor CC if you low aerial 'cuz traction makes him slide out of range of counterattacks - don't always shine, sometimes jump and block are appropriate 'cuz traction
He has poor OOS if you low aerial 'cuz traction
Prioritize putting him offstage over keeping him in the air unless you've got godlike combo break punishes (which is possible, but gimping him is easier generally speaking)
For combo breaks:
U-tilt > his nair combo break
Bair is also good though it trades a lot
For how mediocre u-smash's combo potential is, I don't recommend it (u-tilt leads to uairs and bair can lead to more bair but u-smash is just 18% - if it kills then sure but even then I'd take the edgeguard because hitting bair & nair is so much easier and his recovery is awful unless he gets lucky [and Fox can defend vs luck preemptively with invuln bair so it's not even that good vs him])
If all else fails, shield > something or DD into something (dash attack, grab)
Watch for little range differences or stun differences with dair and fair and whatever but the way you punish them is fundamentally the same, just different timings
If he side Bs offstage to get onstage I find uair punishes **** him at low percent. The damage is great and it's easy to finish with him in a terrible position (above Fox or offstage). I feel people don't combo floaties enough in general but w/e. Otherwise treat it like Marth and bair him off, throw him off, etc. until KO percent (where you u-smash him - if you can send him towards the edge rather than across the stage this shrinks the KO percent favourably [ledgehop to get in front of him and then turn around u-smash])
Uhh, random fact: shine > dash attack is a combo but requires crazy speed but it's useful for when he's slipping off the edge to grab it (after like 50% - sometimes sets up gimps)
And in general I rarely laser in this MU unless he's offstage or something because onstage laser requires giving him space (so laser is safe) and that's when he's strongest as a character IMO because a mobile slide approach with complete option suite is pri goot - I feel he holds hardest to a controlled offense that preys on his traction to cripple his CC and OOS (you're doing what Ganon does except as Fox so it's way better)
Or just platform camp with bair, laser, etc. but that's boring