Find a friend and use RAF, you will hit 90 from 1-90 in, let's say, a week, use Heirlooms (if you have), grind dungeon with your RAF friends, till 80 then throw him into BGs using BGBuddy, once hit 85 you can start using either Questing bot or BGBuddy again, bot 24/24 and you will hit 90 in a blink of eye 
