I tend to start at idle, and incrementally increase revs over several minutes, timed right I usually get a sensible oil / CH temp around the time I get to something roughly equivalent to cruise revs.
Having about 400hrs with Rotax engines, and not yet had one stop in the air, I think this approach probably works.
Incidentally, there's nothing to stop you leaning on the ground to avoid plug fouling, just make sure your checks take you back to rich before t/o.
G