The heart of the walming up problem is the "low tech " oils that aviation still uses most of you are using single grade oils such as W100 or W80 these are not good lubricants when they are cold and so to avoid damage to the engine it should be run at low RPM untill the bottom of the green arc on the temp gauge is reached.
The most common damage resulting from high RPM when cold is worn camshafts , normaly the lobes furthest from the oil pump are the first to have the case hardening worn through this distrbutes small steel particals around the engine , most of them seem to get embeded in the "softer! alloy of the pistons below the rings.
My recomendation is to use a multi-grade oil and warm the engine at low RPM not more than 1200RPM untill 40 C sounds good to me , thease are the numbers for the Lycoming O-540 an engine with a reputation for eating camshafts if ill treated.