Like Mr. Ames...LOL...I'm another electric-to-nitro convert. Here's how I do it on mine for mixtures:
For WOT, I richen it until it won't pull hard, then lean it out 1 "hour" (1/12 of a turn) at a time until it pulls cleanly all the way...then STOP. You'll see really quickly where it needs to be, but always go from rich and only lean it as much as you need to to bet it to pull cleanly. The fast guys may go closer to optimum, but the biggest thing is to keep it "happy" and running nice.
For idle and low-speed, it's a back-and-forth process. To start, set the throttle where the slide is open 1mm or so...that's where you start. Your manual may have a different spec, if so use that. To set the idle mixture...again, tune from rich and just lean it a little until you start to get a smooth pull from idle. Start rich where it blubbers and stutters when you apply throttle and go 1 "hour" at a time towards lean.
Don't get fixated on temperature like some guys...if it's happy, tuned from rich and it pulls clean, then the temp will be fine.
I tune this way on OS motors and I haven't hurt one yet and they hardly ever flame out. Your mileage may vary on other motors, but this should get you in the ballpark and keep it alive during your learning curve.