As others have noted may not be the best looking thing but if functional who cares. It is a glock afterall.
Also I think the job is salvageable if you care about looks. You need to randomize the pattern. A few diff sized heat sources and not
In rows... All over back and forth. That's what makes stippling look like stippling. That is what I found trying it on metal. I would imagine with heat on polymer it will leave a lot of thin edges around each dimple. You could leave these to wear away or buff them down.
Getting skate tape to stick..... First solvent prep the area. Then heat the tape. Apply and clamp. Leave for 2-3 hours.