once you practice a bit you can get really good and boost fast. I boosted 2 teams to 60, the first one was about 30 hours total and the second was about 18 hours total.

in SFK just leave the alts right by the entrance, you can run through aggroing everything, go to the door guy (in the prison cell), open it, agro everrrything inside until you are "above" your alts after the 2nd or 3d boss (the guy in the room with the bats), right after his room i stop right above my alts, its all the ghost humans, kill the ~100 mobs or so in 2-3 mins with just consecrate, and blammo, 1 level in 10 mins with RAF 3x (it takes longer without RAF).

At 20, go to SM cathedral, leave alts parked at door, and pull everything outside the cathedral doors back to near your alts (but not too near!) and consecrate down. You can then have your alts follow you inside, park them at the top of the fountain near the back, and pull the boss inside the cathedral out the door and just kill everything off to a side. Should take 10-15 mins per run, and again with RAF you get nearly an entire level every 12-15 mins. All the way to 40, after 40 its frankly easier just questing although you can do brd, lbrs, and strat/scholo after 45.