Brian,
No secrets; maybe just lucky!
I use 10/22 (50/50), metal uniflow (no exhsut pressure), stock muffler, various props and 2 layers of the thin part of panty hose material ever the venturi. We are about 250 ft. above sea level--if that matters, near Montgomery, AL.
When I fill the tank, I use a hand crank pump and make sure that I get a drip or three from the venturi as well as slight flow from the tank overflow. Then I choke with a finger 3 or 4 revolutions---make sure there is fuel on my finger after choking. Attach battery, pull thru until I get a bump--usually one or three blades, then flip. Usually one to three flip starts---if it seems a bit wet, I will back flip for starting.
Very seldom will the engine need more than a flip or three to start, with a hot battery. Usually use a Thunderbolt RC plug, but have had good results with the OS LC3 (car plug, but very hot according to OS heat chart).
Cheers,
Jim