I have previously stippled the detachable backstrap of the M&P9 with a soldering iron. It added some grippiness to the gun, but one a big portion of the M&P9 that is part of my “grip” is still very smooth (e.g., the portion that meets the meaty part of the palm). So I finally went for the full frame with a wood burner (fine tip).
For the ‘scale’ pattern that was used for the M&P backstrap, the soldering iron did the job alright (picture above). However, I wanted a finer pattern for the actual frame. So I got a wood burner with several interchangeable tips. It is a $18 investment.
Before I decided to stippled the whole frame, I went with GT-5000 grip tapes. It added a bit of grip, but it was prone to shifting a bit and still not as grippy as I would like to be. So I figure I’ll go for stippling the whole gun.