Light it like a cigarrette... inhale slowly... (clean bats need little, the dirtier, the harder you need to pull) Use the shiny metal part of the lighter as a mirror and see if your burning, if not, light it again. Try to keep a nice even pull, don't pull too hard at the end or you will eat ash... Listen carefully, you will hear the resin burning away (slight crackling) inside the bat just as the last bit of weed is smoked. Blow it out and tap it with your lighter to clean, repeat, enjoy.

I use a q-tip and an aclohol swab pad to clean my bats, gets them almost new looking without much work.