if you do all that correctly then you would avoid all grab attempts he tries to go for which is most important. DON'T let him grab you or you'll end up at like 50% off one grab. Thankfully Fair and needles do the job really well though.
With Luigi being all about grabs and setting up fireballs into grab, I have to wonder if it is better to go for retreating fairs as he rushes in for a grab, or if spot dodging is the better option. I've had mixed success with both. And it's really the only thing that I have a bit a trouble with in the Luigi MU, as it is very much in Sheik's favor.
If you spot dodge the incoming grab, they can wait it out and punish you for it, which I've been getting a lot. If you try to roll, there's a good chance a decent Luigi will read this and, again, punish you for it. If you go for a retreating fair, or at least sometimes when I do it, they are often able to just bumrush it and grab me anyway, provided I don't immediately throw it out after the SH, in which case it won't be autocanceled, which gives them several options. Also, simply short hopping away allows them to grab you on the fall. B reversed needles would work if he is a good distance away, but in that case he wouldn't be wise to go for a grab in the first place. Doing so in potential grab range would leave you open for a punish. Of course, you always just completely jump away, but that's not gonna give you a chance to punish their grab attempt and you don't really want to be above a Luigi.
I know the best answer would be "don't put yourself in this situation", but unless you're a robot, you're gonna end up in this situation from time to time.
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Also, lately I've been having trouble with good Yoshis. He is just such an overwhelming character, I think he is by far my most feared matchup, even more-so than Rosalina or Sheik dittos. How have you guys been dealing with this green powerhouse?