I like that 'roller' you used, no reason it wouldn't perform well.
The trigger set screw is doused w/RED Loctite and that's why you're having a tough time removing it. I should have mentioned it in my original post. So it definitely will take heat- mine did- and I used the exact same method you mentioned, a soldering gun
in my case. In fact, if you look closely you can see a small spot of solder (circled below) that adhered during the heating of the set screw and trigger! Next time I have it apart I might remove it. Or not. ha
I have the grip off now, I don't like how it feels. Also have some stain coming. Hopefully I can whittle it down into something that feels better to me.