When I started in the hobby in the late 90s, they were still using CI engines... you know, the ones on the control line airplanes where you flip the prop while closing the head screw till it starts?

Having done that, my technique for starting engine by hand flipping is good. In fact I never even used a chicken stick or starter for the first 1.5years of RC flying and never got a knuckle rap (I have been flying for 3 years now). You wont get cuts if you are using a 40 or 50 class engine provided the engine is vertical, throttle is set properly, the trailing edge of the prop has been de-burred and you use the correct technique (the biggest one I started was a 61FX on a trainer).

But last year I tried to start a inverted 75AX by hand and got a nasty cut when it back-fired. That was the end of that. Now I use a chicken stick even of a 55AX. I value my fingers more now. I flip it a few times with the stick and if it doesnt start, use a starter. As I dont have a vehicle yet, I cant carry my starter to the field, I usually get a starter (and a lift) from someone else. Note that my instructor still uses his fingers even on the 120 sizers without any cuts; he doesnt even wait till it stops turning after a flick if the engine has not fired...guess some people know what is happening a lot better and faster.

In conclusion, atleast get a chicken stick

Ameyam