This article by Craig Anderton on HarmonyCentral is about multi-band distortion. The technique behind a mutli-fuzz is to split a clean guitar sound into four or more frequency bands and distort them individually, which reduces intermodulation. This technique is similar to the hexaphonic fuzz first popularized with the Roland synth guitars with their hexaphonic pickups.

Some DAWs include plugins for multi-band distortion. Apple Logic Pro doesn't include a multi-band distortion effect, despite it's incredible array of virtual intruments and effects. But it's not hard to set up Logic for this, and it sounds absolutely HUGE:

multifuzz mixer layout

Track 1 sends its mono output to Bus 1. Aux 1-4 are each getting their inputs from Bus 1, doing their EQ and distortion, then panning their mono outputs into a stereo Bus 2 (but this could be Out 1-2 if you don't need any plug-ins after the multi-fuzz).

Play with the EQ ranges. Play with the guitar amps on each of the ranges. Play with the panning.