Ultimo-Hombre, I owe you a debt of gratitude. After doing much research online about doing both the grip work and silicon carbide grip job, and finding a disappointly small amount of info on each, your write-up ended up being my guide for the project. In case you were curious and for anyone else considering this, here are some thoughts/things I encountered when I did this project.
I have a Gen3, and the texturing is in recessed areas (front of grip and backstrap), so I was concerned that smooting everything flush with the bottom of the recessed areas would leave the grip pretty thin. Fortunately, this wasn't an issue. I went slowly (per your recommendation) and carefully and I was able to smooth everything flush. The side panels on the grips actually extrude on the Gen3, so I blended the edges of the raised area with the rest of the grip, and took the sanding drum to rest of the raised area to smooth it all out. The only tough part was working around the Glock logo on the left grip panel, I just went slowly and I was able to work around it.
The thing you mentioned about masking tape made a big difference. I'd usually buy the cheap "Ace" brand stuff, but I shopped around for some good stuff. Went with 3M "Edge Perfect" (or something like that) masking tape, meant for fine detail painting on trim, etc. Packing claimed it would leave perfect lines at removal. So I actually spent $7.99 on a roll. Absolutely worth every penny. Pretty much followed your masking instructions and used a hobby knive to cut nice rounded corners. When I removed the tape, it did leave absolutely perfect lines. Worth the investment if you are as OCD as I am about getting stuff "exactly right".
Also, for some reason the 3 or 4 stores I went to didn't have JB weld. I've had good luck with 3M Epoxies, but since JB worked for you, I'd rather go with what I KNOW would work. After my failed attempt to find JB weld, I ended up with 3M's Slow-Set 60 min working-time epoxy (comes in a double tube syringe so you get a equal mix of the two parts). I tested it on something first and it seemed to work well. So I made a big mix of it on a paper plate and started spreading it around the grip area. I then used some small foam paint brushes to smear the epoxy around the grip, over the edges, and get a nice even thickness and coverage. It ended up working out great. Before I started, I got some bailing wire and made a hanger to hook on the trigger guard so I could hang it when I was done. I was glad I did, otherwise I would have ended up with a epoxy and silicon carbide covered gun in my hand and wandering around trying to figure out the best way to let it dry. Anyways, the 3M stuff worked well.
After I checked on it this morning, the silicon carbide looked great, but was VERY rough. After being sure the epoxy was very well set up, I took a 200 grit sanding sponge and lightly sanded all the silicon carbide surfaces. This made a huge difference and smoothed it down enough that it's very gippy, but not nearly as harsh. Overall, I think it turned out better than I could possibly have hoped for a first try.
Thank you for sharing your process! I would not have attempted this based on the other online guides I found. Once I have the pistol all back together later today I'll post some pics. Thanks again!