I remember seeing my Dad start his inboard boat engines with his thumb on the flywheel bumping against the compression. I always thought this was too cool! Mostly he used a leather shoelace that would grip in the flywheel groove. That was before electric starters. When I was flying controline Combat models we went to using very thin speed props that you could not flip the engine through compression to start it for fear of breaking it. We would position the right side of the propeller up against compression and with a bit of prime in the exhaust and the battery connected, take 2 fingers and hit the right side of the prop downward, which would then "bounce" off of compression, firing the engine. AHH, the good 'ole days!
Dick Tyndall