I haven't done this since the poker boom for online cash games and I have trouble doing this even at playchip tables now but you would have to be a winning player at one table first with a sound strategy that you could look at a random table with a glance and know where you are in a hand.
The first step would be starting hand recognition then the next is being able to judge a flop with a glance then the next to know exactly what you're looking for in the next streets. And what a lot of folks don't get is its all preplanned by the starting
hands. Then its just a matter of practicing with more and more tables. You have to get used to playing and responding in a timely manner at the tables and it only comes with practice. Once you can do that and you're a winning player then you can add more tables.
You can do it with holdem but its a lot more involved when you do it with the stud variations like razz, stud8 and stud because you have to keep track of cards on other folks boards so its more difficult to play more of the stud variations than holdem because it requires more memorization.
If you're a losing player in whatever you play then you will lose more money doing this so you have to be honest and know what you're doing. Some people will play better with more tables because they get bored with one so its really more of a psychological thing than anything, but again, you will have to honestly judge your play and that of your opponents to see if this is the best thing for you to do.