Using a crescent wrench is a little better than the glo plug wrench but still not good enough. Use the box end (the closed end) of the exact correct size combination wrench. A 6 point is best but a 12 point will also do quite well. Also a good quality wrench, Snap On, Mac, or Craftsman will allow you to get the nut tight enough without rounding the nut. A couple drops of blue Loctite, then install and torque the nut. Using a hollow cone shaped spinner, either plastic or aluminum, will transfer the torque of the electric starter to the drive washer of the engine instead of directly to the hex nut holding your prop on. The electric starter is spinning in the direction to loosen the hex nut, sorta like an impact gun removing the lug nuts on your car but without the hex socket. I also find it difficult to use an electric starter on a plane (that would be someone else's plane because I won't set one up that way) that has no conical spinner and just the small hex prop nut that comes with the engine. I don't understand why some people do them that way. If the plane's style calls for no regular large O.D. hollow spinner and you're going to use a "spinner nut", then either a matching locking nut or a good helping of Loctite + making it really tight is a must. For 4 strokes the two OEM locking nuts is best. I have done a couple of 4 strokes with just a well tightened Loctited spinner nut but it can be risky as a 4 stroke will sometimes run backwards when you are starting them up and if the nut were to spin completely off you now have a flying nut and worst of all a spinning propeller not attached to anything. No lock nut on 4 strokes is not recommended. Also if you are using a wood prop, no matter what style spinner or spinner nut you are using, they must be retorqued after a few flights. The wood will compress and you must reclamp it down down to maintain nut tightness.