When they start to run just like your finger and wipe it on the leaf where it's running - and then take the lighter and burn the bit that's slow - that should even it up. Once your about half way through, maybe even less than that it should stop running anyway.

I'm not sure about the microwave thing - although i've enver tried it so i cant really comment, it just seems to me that it'd dry the leaf out so much it wouldnt roll.