Regarding stuffing a rag into the exhaust ports to prevent crank rotation, my Clymer's manual states that is not a good idea because it can cause the rod to bend, so, in my opinion I would not do that.
The reason I suggested using a chain wrench was NOT to remove the PTO, but to secure it while you turn the MAG flywheel nut. (you will definitely need two people, one holding the PTO and the other turning the MAG flywheel nut.
I took my MAG flywheel nut off lickity split using a impact wrench. (Clymer's also warned not to do that, however, I did not see the harm, so that is what I did)
If you don't mind scratching the paint on your PTO flywheel, you can also hold it with a large pipe wrench, however, you will definitely nick it and and have to repaint it unless you put some rags on it to prevent the pipe wrenche teeth from digging into the PTO.
If you use that precedure, be sure to remove the small Zerk fitting
Since you don't have your engine out of your Doo, it may be difficult getting an impact wrench between the gas tank and the MAG, so I strongly suggest using a chain wrench or the PTO tool. The tool can be ordered on e-bay for about $15. In fact, the guy that sells it lives about a 1/2 from me and I found him dependable.
