ssym don't ever feather the gas while doing a burnout. Your causing the stater in the converter to engage and disengage. It won't last long. I've never had to use a line lock.
My opinion would be to roll barely thru the water. Hit you gas hard and fast to about 3/4 throttle. Shift to high gear as quick as possible. As you feel the rear tires starting to bite go ahead and roll the gas to full throttle. Its very important to hit the rear tires hard otherwise your ass end will start to drift from side to side.