I stipple M&P grips, mag releases, frame tools, basepads, and the striker plate. I wanted to stipple things I could replace...rather than frames. This way - if I wanted to sell the guns, I could put factory items back on.
I tried 10 different patterns on extra parts before I settled into what I liked. I use a wood-burning tool and a couple different tips which come with the tool. If you do try this, make sure you have adequate ventilation and wear a ventilator. I wore a surgical mask for the first year...that was the wrong answer.
Here are a couple of my products. Remember, every frame, every part will stipple differently. I cannot stipple PMAGs - they look like crap after I try. The plastic is much harder than the softer parts of a M&P. Just my experience.