I've also used that method before. Older neglected rigs mostly, where the grease had contaminants inside the zerk orifice. I have also created a nice little scare with small flames. It might not bother anything, but I would be a little concerned doing that on these type joints vs. A rubber bushing. I just don't know if the heat would hurt the plastic race. At the same time, a lighter should suffice. I know you aren't holding heat on it long enough to start tweaking things. Sometimes I don't recommend some quick tricks when wrenching. Where some guys have years of experience with lack of special tools, using their head and what's available (successfully and safely). Others lack that thought process, and common sense. Believe me, there are guys out there that will get it red hot and melt something, or burn down their rig, garage, and half the neighborhood. Unless I've read numerous posts from a guy proving otherwise, i assume they are still green.
Btw, I do realize my grammer in my posts sucks, and things get jumbled. This windows phone doesn't play well with GATR. Im glad Blaine made time to explain the workings/design of these things. I really find it hard to bank on "Jim from RE" really knowing what he's talking about. So it puts my mind at ease talking to a big player in the offroad game. For those who aren't familiar, he owns/operates black magic brakes, and has his hands in savvy stuff as well(just to mention a few). I also didn't hang up the phone with $1k worth of arms being shipped. I figured I would at least share the knowledge.