One of the keys is a good hard aggressive flip, not a lazy half hearted one. A lazy flip can catch you, especially if the engine is a bit over choked and somewhat flooded. The engine will backfire and slap the back of your hand/fingers and it will hurt like h e l l. I have a good leather welders glove that I added thick stiff foam rubber protectors to each finger top. I only use it on new engines I am unfamiliar with though..... Otherwise I get lazy and don't bother with the glove like most people.

As far as sharp edges cutting the bottoms of your finger, the APC or the carbon fiber props are the worst for that. The wood props generally don't cut you and I feel a lot safer hand propping them.

Do be careful though. I've seen some horrifying pictures of injuries from hand propping engines. Also take your time and think clearly. One time I was adjusting an "unhappy" .40 size glow engine. I had to keep adjusting and fooling with the engine, and I was in somewhat of a hurry. Finally, in my rush, I reached right through the prop arc to make an adjustment. The engine was only a .40 glow engine, and it was only idling, but it still cut several fingers right down to the bone, including three of them right through my finger nails!! []

AV8TOR