For in car break in:

1.) Warm the engine with a heat gun until it is (around 200F).
2.) Start the engine. Then establish a rich idle ( around 7,000 r.p.m.)and let the engine run for 150cc of fuel, then let the engine cool to ambient temperature. Running temperatures during this stage will be between 190-200 degrees F.
3.) Next, with a fully engaged clutch, run the car at a very rich setting for about 750cc of fuel. Make sure the car is very slow at full throttle, and lots of smoke at this stage. If the car wants to go fast at this stage richen the main needle until the car makes lots of smoke, but does not move fast. Maximum R.P.M should be about 15,000 at this point. Let the engine cool again. Running temperatures during this stage will be between 180-200 degrees F.
4.) Over the next 750cc of fuel you can gradually lean the high speed needle. A good method to keep in mind is to go one hour leaner per tank of fuel to be safe. The engine will need to be run at a race setting in order to become fully broken in. Each engine will break in at a different time, and with a different amount of fuel due to differences in manufacturing materials, tolerances, etc... You can know that the engine has fully broken in when you are running the engine at 90-95% of it's potential, and you can run at this pace without the engine going rich. An engine that is not fully broken in will continue to richen itself on the racetrack.
An engine that is properly and fully broken in will reward you with cooler temperatures, more power, and long engine life.

For Break in using a propeller:

Always keep the cooling head covered so the airflow does now cool the engine too much. You can use aluminum foil for this.
1.) Warm the engine with a heat gun until it is (around 200F).
2.) Start the engine. Then establish a rich idle ( around 7,000 r.p.m.)and let the engine run for 150cc of fuel, then let the engine cool to ambient temperature. Running temperatures during this stage will be between 160-190 degrees F.
3.) Run the engine at 1/4 throttle for 450cc of fuel then let cool. ( Temperatures should be around 200-210 F)
4.) Run the engine at 1/2 throttle for 450cc of fuel then let cool. (Temperatures should be around 200-210 F)
5.) Run the engine at 3/4 throttle for 450cc of fuel then let cool. (Temperatures should be around 200-210 F)
6.) Run the engine at full throttle for 450cc of fuel then let cool. (Temperatures should be around 200-210 F)
7.) After this process has been completed on the break in bench, it is time to install the engine in the car, and follow the steps listed above from # 4 until break in is complete.

In reference to the WOT break-in I have used it with the same success as the idle method. I think the most important thing is to have the engine rich and getting some temperature into the engine in the beginning. If you let the engine sit and idle too long it can damage the engine just as you can damage the engine from running them too cold.