I fly a Yak-52 and echo everything already said about the M14-P, but once when sitting in the AC on a very cold day waiting for the temps to come up, I had the owner of my maintenance org and supplier of the plane in the back and he suggested pulling the prop back. His words went along the lines of it would make the engine work harder and warm up quicker.
Has anyone come across this technique before, either for radials or other types? Though the actual RPM is going to be low the engine will be under a relatively increased load before it's warmed up. I must admit I don't do this, preferring to do it the hard way - waiting!