I learned this trick on my own and here is how I went about it.
1st) I got comfortable with a regular stand still burnout.
2nd) I started trying to do a rolling burnout, at a slow speed.
So I would put some pressure on the front brake and add a little throttle. Putting your weight on the front of the bike by leaning on the gas tank is ESSENTIAL. I tried this without my weight on the front, and the bike would kick to the side everytime!
So lean forward, apply brake, give some throttle.
Practice until you have the right balance between the three. I remember my first time. I didnt even know I was doing it until I heard the rear tires screeching through the parking lot. I was like Holy Sh*t! It was sick! and its been a blast ever since. once you get a rolling burnout down packed, the donut burnout will just follow.