I used to multi-table limit holdem at pokerstars, i deposited 25 there and grinded up to 2k in about 2 months before black friday made it up to 1/2 while taking shots at 2/4. I regularly played atleast 6 tables and up to 12. Limit holdem is different though since once you have played enough you can make decisions pretty instantaneously, I don't think I'd be able to multi that many tables on NLHE and especially not PLO, but once you've played enough hands the decision making process does get a lot faster.

My rules for multitabling are:
1) be over bankrolled for the level that you are playing
2) warm up first by gradually adding tables
3) try to have the tables set up so they are clearly visible on your screen (need a big monitor or multiple monitors)
4) have all your open tables be the same game (i.e. dont mix NLHE, LHE, PLO, etc.)