Ableton is
the best tool on the market for this job.
First, learn all about warping. When I import tracks and set up the beat grid, I always do it up against the metronome, to make sure it sounds tight, as well as looks like it on the display. If importing from CD, you can usually just set beat 1, then fine tune the bmp. If you've sampled in from vinyl, you'll probably have to set warp markers every 32/64 bars to keep things tight. Depends on how stable your decks are.
I would recommend using 3 audio tracks in the arrangement view, with the first 2 representing your 2 decks and a third to overlay additional samples.
some further tips.
set up a high pass and a low pass filter on each track, automate them - it's fun.
set up interesting delay lines on the FX sends, then draw in short spikes into the FX send automation on tracks to echo off small fragments of tune/vox/samples.
here's a great lazymans tip for using DBlue glitch (best free plugin in existence) leave it on random, and set it at 0%. Whenever you want a weird break, turn glitch up to 100% for that bar/segment. If you don't like what comes out, change the seed value for that bar. repeat until it does something that sounds great.
I have a tutorial on the way filled with more tips and tricks, but in the meantime, if you'd like to hear some results surf to:
http://www.chelfyn.com/Psychelfyn_1_Astral_Raveling.mp3
http://www.chelfyn.com/Psychelfyn_2_Show_Dont_Tell.mp3
http://www.chelfyn.com/Psychelfyn_3_Dream_It_Up.mp3
All of these are psytrance/breaksy/harddancey mixes done in ableton, with liberal over-use of long voice samples from films. Ableton makes it easy to pitch match everything, and also to make the voice samples time out perfectly over long breakdowns.