By alone I hope you mean you're the only one in the water - but that you will have a buddy on the boat/dock to assist and monitor your safety.
Some transmissions will lock the shaft, but only to an extent as Jones indicates. The pipe wrench is a bit brutal but will avoid stressing your strut if you need to put a lot of torque on the puller. Blocking the prop against the aperture or hull may transfer the forces to the strut.
Tapping the shaft with the puller tensioned is a great idea.