Just lean it after start
My procedure for engine warming is idle plus lean mixture. That way, I don`t get fouled plugs.
I strongly recommend everone to always lean the mixture after start until the run up. But if you pull the red knlb, pull it hard. You must have the mixture so lean that the engine will immediately quit when you apply takeoff power. It`s safer to pull hard than being timid and forget it leaned before the takeoff.
The mags check is much more valuable if you do it with the mixture leaned. With the mixture leaned, any ignition problem will show soon, before it gets worst. Doing this, I learned that, if a standard rich mixture mag check shows a discrepancy, you have a big problem. With the mixture leaned, the problem shows earlier.