Arlin,
I use a big waterpumpwrench and a solid vise. I have aluminum jaws I put between the vise jaws and the barrel. Make sure the entire portion of the barrel that is tapped for the breechplug is not clamped in the barrel, but just sticking out a half inch or so. You dont want to squash the threads when trying to install the bp. Most new bps have parallel sides to hold the wrench. This is good and bad as it is easier to get a good hold with a plain wrench such as the one you have, but it is harder to get a good inletting job. The old ones were tapered narrower at the bottom to make inletting easier, I guess. In any case adjust your wrench so the end of the jaws are a fraction of an inch from the top of the tang, so any maring will not affect this crucial area. I use antisieze compound, some others use other stuff. Make real sure the threads in the barrel and bp are very clean before you lube them with the greasy stuff of your choice. A very slight maring of the barrel is not unusual, and can be dressed up before you brown or blue it. Good luck. Frog