There is as many methods as there is racers or bashers...

I just broke in mine last week. I let the engine run on the starter box very rich but at 180F for the whole first tank. I shut off the engine before the tank was completely empty to make sure the engine was not running lean. Let the engine cool down with piston at BDC.

Restart the engine and lean the settings slowly (1/8 of a turn) at each tank for the next 6-7 tanks. I've ran the engine slowly, about 1/4 to 1/2 throttle. I also let the engine cool down with piston at BDC after every tank. Once again, I've stopped the engine before the tank was empty.

When the engine was performing well and I was happy with the performances, I concluded the break in process was completed. This is after tank 10. However, I will not abuse the engine for many tanks. I progressively run it harder.