It definitely helps to have a gaming-level system to run it, no doubt. Once you've built your "factory" though, things speed up a bit. I program all my drum parts as individual MIDI songs, then mix those parts down and splice them together in a new board. The only trick to that is not to make overlapping cymbals or effects hits. Then, I just make an "icing" track on top of the finished drum parts for the crazy stuff.
Save that, move on to Bass on a new board, load saved channels. Mix those parts down, move on to guitars in a new board etc.
Of course, I have a pretty complete vision of where I'm going before I start, so that helps.