If you're DBing a duo, make sure they are both doing quests. It's a waste to grant levels to the guys you're playing with. I use Jamba, which makes this fairly simple. Sometimes I click in other window for quests (non-sharable). Otherwise I just share quest and slave is set to auto-accept. Pretty nice.

As for faster, instance boosting is beyond light speed. I went from 40-45 on two guys in about 90 minutes or so doing this and both guys are one day old and this is my first time (lots of mistakes). The next time around will be probably 25-30% faster overall.

Trick there is you either need a friend that's 80 to do it, pay someone to do it or do it yourself (3 accounts).

I often see people in /trade willing to run stocks for 15-20g a run. If I didn't have an 80, I'd cough up the gold for a few runs to go from 15-20 in under an hour. Same with SM Cath, et all.