Don't grab the spinner on a backwatd running (or forward) engine. Its not safe.

The trick can work... but with small engines, you got small spinners, and you will end up sticking your hand in the prop. When you get to a larger engine with a larger spinner, you gotta grab harder, and there's mor torqu, you can end up breaking a finger on the spinner, never getting it in the prop itself.

Use an electric starter and backward running is virtually impossible.

Use the backflip hand start technique and backward running just doesn't happen either. Set the prop (when installing it) at parallel to wing when the engine enters compression FORWARD, rotate backward till it enters compression, flip downward, with fingers barely contacting prop, when engine kicks, fingers spring off prop, and the engine fires forward. Very safe, very predictable.

Never prime an engine with the glow plug connected... they bite. (I found that one out the hard way 25 years ago)