Acid isn't all that great for this ... actually it sucks a boat-load of ass for DJ mixes.
Use the event specific pitch-shifting features in Vegas to to DJ mixes. It works very well, and I've done ~15 tracked mix CD's like this. You can get very creative, adding your own breaks, effects, samples, etc. Quite fun, in fact, all in ~4 stereo tracks.
Right-click on the event and select properties. Use the drop down menu at the bottom of the "Audio Event" tab to select "change length & pitch". Then adjust the pitch in "cents" to change the speed. It's even more accurate than a pair of CD decks.
For small nudges, just slice the event on the beat and slide it back a little. I also suggest applying non-realtime EQ to cut the lows on one or both of the songs you're mixing during the mix so that the bass doesn't get phased or over-powerful. Just use the EQ like you would on a DJ mixer.