The egg crate trick worked great for me in the past. I used to keep new tangs inside an egg crate enclosure until the old tangs got used to seeing, smelling, tasting? the new fish. Sometimes it only took a couple of days. Once it took a couple of weeks. Then I release the new fish and there is minimal chasing around because they've all had a chance to get used to the newcomer beforehand.
Good luck with the MI. I had one back in the 80s in my first fish only tank (not a fowlr since I didn't know what live rock was and you couldn't find live rock in the LFS anyways). Once acclimated and eating, I found mine to be very hardy. Only sold him off because I had to shut down my 110g and concentrate on my university studies
