This is where having hardware sequencers, jamming everything Live, recording into soundforge and editing it down really comes into its own, you just end up with 7 or 8 minuits of audio to edit down, so you can pick the best bits out and wedge them all together....
Like you know how a track can sound so good when it's just a loop, i.e. unarranged, you can capture that moment and vibe, and then sort out the arrangement later...

also I find if an idea don't work within a few hours scrap it, cos it ain't ever gonna work.... if it rocks, it rocks...