I would think a lesson on starting precedures may be in order here. I hand start my OS160FX, My Zeonah G26, and my Roto35 and do not have anything to show for it other than the engines running.

Scars on fingers/hands in that short of time indicate to me that improper methods are used to start and hand prop/chicken stick.

Just a very quick overview

Prime as needed being careful not to over-prime. No priming usually is needed for a warm engine and never prime with the glow ignitor connected
Prop should be set so the blades are at 1pm (right plane facing the plane) and 7pm (left blade facing the plane) just as the engine is coming on compression (glow and most electronic ign. gas engines)
Now while facing the plane with the prop blade at 1:00pm/7:00pm postion against compression, flip the prop to the right with the right hand swinging you up and over the top of the prop arc from the 1:00pm position. your hand will swing up and away just as the engine comes off compression and your hand will be clear as it fires. If it does not fire, wait for the prop to stop moving before trying it again. Sometimes the prop will swing back against compression and actually start the engine and if you reaching in there to grab the prop then you will get bit.

Never use the left side (facing the plane) of the prop as you are now going down with the prop arc and it you slip you can be sure of a prop srtike. It's uncomfortable at first, but it works well.

OS160FX engines are usually started by "back flipping" the engine. I prime mine if needed, grab the spinner and give in a quick "bump" in the wrong direction (backflipping), it will kick back the correct way and usually start on the first try. So see some engine actually work better that what you would normally need to do.

The key is to never go down with the prop arc, but always go up and away with the prop arc