Originally Posted by Robotech

I just used a product called Sugru to modify the grip on my Ruger Mark III Target pistol. I wanted a support for my trigger finger for consistent positioning.

The black Sugru matched perfectly the silicone color of the Hogue target grip, and is a fairly close match for the M&Ps.

I was also able to texture it once I got the shape I wanted, in this case using a plastic tube from an air-duster can. You actually have a fair amount of working time to get it right. I used non-acetone nail-polish remover to clean the grip surface first, and a water-wet finger to smooth things out.

The only problem is that Sugru is a bit expensive. This support took nearly a whole 5g packet, though it is thicker than you'd likely want to customize a the body of the grip. You'd probably use three or more packets for a Shield grip.

If you do an Internet search you'll find several examples for using Sugru for pistol grips, including some simple ways to texture it.