If you're going to bench run it, all you need to do is provide good airflow through the cylinders. A big fan at high speed will do for longer runs. Keep a heat gun handy so you can track the temps. After setting the high and low needles to where you want them there's no need to run at max rpm. Half throttle for short periods, 80% os so throttle for shorter periods, then a little above idle for cooling periods. It's all about heat cycling and it will take about 3 running hours at varied throttle settings and temperatures to complete the cycle. In the air is the best and easiest way, but on a bench makes some feel better about adjusting the needles. Unfortuantely many engines change once the cowl goes on and you have to start all over again.

The only item that's being broken in is the ring(s). The rest is thermally bringing the casting together.