Let's say you just shut down the engine by setting rpm to 1000 and did another mag test checking for grounding, then pulled the mixture and now shut off the key or better yet, shut off the mag switches and then the master.
Now you have tested the mags, closed the throttle, mixture is to cut off, key is out of the switch and the master is off. The master doesn't have anything to do with this process except keeping the battery fron going dead and cutting off the starter.
Now if the prop IS AT the 10:00 position when you are ready to connect the tow bar, then just move the prop DOWN to the 9:00 position. You will not hear a mag click!! If you do, then something is wrong!
Just a note here....... Key switches, I hate key switches. They do nothing to secure your aircraft, and they are a maint problem. When they go bad, they remain HOT MAG with the key removed!!!! When you move the key to OFF position you will notice that the key will move about 1/8" more, as the switch wears, it will become hot there!!! You just shut down the eng. with the mixture so when you shut off the key and removed it, the mags are still HOT. There is an AD out for this. I found this out way before the AD.
Warren