Except, probably the rear entry pipe, the trigger guard is my least enjoyable piece of furniture to finis and inlet. I discovered that doing it in two steps is, for me, the mose efficient.
First I bed the TG in a piece of 1/2" thick wood long enough to be able to cut the approximate shape of the TG. I slather on a batch of Bondo along the wood pattern profile and bed the TG in the bondo. Try not to have any Bondo smooshing up and over the TG. Some will - it's hard not to. I've learned to use as thin a piece of wood as possible so I can work the convex complex curves inside the shape of the guard. Set it aside overnight.
Now you can hold the wood piece in the vise and go at the inside of the TG with files, scrapers, and sand paper till it's as finished as you want. When you are finished heat the TG with a heat gun or propane torch and it will drop right off the bondo. It stay's hot for a few minutes unless you drop it in water.
I repeat the process using another piece of wood and bondo the front and rear fineals onto the wood. If you are working too hard friction will heat the metal enough that it will part from the Bondo, so take it easy.
That's how I do it
