Your idea of starting at low engine speed on a water-cooled engine makes some sense. But if you are running a modern multi-viscosity engine oil (especially in an air cooled engine that warms very, very quickly) then lubrication is almost instantaneous. The days of engine warm-up died in the 1970's.
I have a Craftsman 18 hp horizontally opposed lawnmower that I bought in the early ninties that I estimate has over 3,000 hours on it. It still works and I use it occasionally to cut the grass but I've replaced it with a John Deere just because I wanted something newer and was tired of having to weld the frame back up. I always started it at a bit higher than idle rpm's then bumped it up a bit to move to where I would start to cut. Then after engaging the blades would bring it up to full throttle. This is a gear driven mower.
It still doesn't smoke or burn any oil and I've always used the straight 30 weight oil they recommended. I've read before that 1,000 hours is what you can expect out of an air cooled engine so either Briggs built this one really good or what I've been doing is working. I've been doing this all my life and I'm 61 now. The only time I don't is because I can't by design, like my generators and pressure washer.
I'm not trying to be argumentative, just passing on what I believe has worked for me for many years with no apparent downside.