Airplane engines usually get excellent cooling. And we run fuel that has more oil than cars, I think. Nobody I know uses a temp gun because it won't record the inflight temp (unless you are very tall and very fast on your feet). People who fly 4cycle should probably use tachs but 2cycle engines are easy to needle.

Most new 2cycle engines nowadays are very easy to break in and have the lowspeed needle set almost perfectly for the initial flight breakin time. Matter of fact, an experienced modeler can key off of how the engine transitions to know when the flight breakin period is complete. There is usually a technique mentioned for the first couple of tanks of fuel run through the new engine. Setting the highspeed needle is part of that. Then you fly with a rich highspeed. At some point in the initial flights, you'll notice the transition gets a bit hesitant. The engine has started to free up and the rich lowspeed that was perfect for the first flights is now just a bit rich. You make sure by doing the pinch test, but they're almost always a touch rich. And the pinch test helps you set them perfectly. BTW, do it right before the first flights on an engine to insure the low is rich.