Tune the engines separately. That is, start one, tune it, shut it down. Then start the second one and tune it. Tune them both as you would if they were singles.

Hopefully, the throttles are proportional and synchronous.

If you lose one engine, you can expect it to yaw quite a bit in favor of the running (that side will lead or be more forward to the other side causing a yaw in flight). Some of this can be corrected with the rudder, but get it down as quickly as possible. A dead stick with a twin can be a bit of an experience when one engine is still running.

Good luck with that Twinstar. They do sound neat when flying. I've flown one and it was a true speedster. It had a pair of .36 Evolutions on board. A real powerhouse.