I had the same problem with two units in my home. One was very stubborn, the other extremely stubborn. On the brass shaft, I added a washer that covered the brass body, then lots of washers until there were more than the shaft could hold (about 1/4" more). Finally added a washer that was large enough for the screw but smaller than the screw head. I added the screw and screwed it down until the cartridge moved, then adjusted the washer setup until the cartridge was out as far as the washers would allow. I finally worked on the cartridge with pliers until it came out.

The reason Moen cartridges are sometimes stubborn to remove is that the "O" rings swell and lock the cartridge in. While Rancher guys method may work a easier way would be to rent or purchase a Moen Cartridge Puller, (see image) Regards, Tom