Multi-tabling really is an animal all to itself. A lot of people recommend books, but they won't directly address the style of play that you are going for. The reason being that there will always be some reliance placed on opponent reads.
The way I learned to successfully multi-table was trial and error with many different strategies until I found one that worked - playing as many as 10 tables simultaneously at limits even higher than the ones you are currently at.
You can read about my multi-table play on my blog linked below - even learn my specific strategies. If you go at it alone, my best advice would be keep accurate data of your play and utilize PT to really assess your play and your results with various hands. You may find it useful to maintain different databases for each different strategy that you experiment with.
I wish you the best of luck!
The Greedy Gecko
PokerGreed Blog