PWM RGB 12v LED strips in chasing patterns.

Hello, I've got a project I'm having great troubles getting to work and I'd appreciate someone telling me whether I'm looking at something feasible or not.

Basically I want to have RGB patterns between multiple RGB lights. I'm having trouble getting code running for 2 RGBs at the moment.
I have figured out the powering of the LED strips using mosfets to hook up the arduino.

Here is a thread I made in the LEDs and multiplexing forum: http://arduino.cc/forum/index.php/topic,55390.0.html
It explains where I'm at and what I've done.

One problem I can foresee is that I want to scale up to controlling 6 RGB lights independently through code. I'm going to run out of PWM pins before I get that many hooked up. I've heard about 'bit-banging' pwm on the digital pins and that I believed would be suitable for what I want to do. Am I correct on this?

Any help is very much appreciated, I'm going crazy frustrated trying to work this out on my own.