I'm trying to make a shading in blender 2.8 that looks like the handle of the Glock
like in the picture
I would go with a Noise Texture, softened by mixing with white. I would also give a small subsurface value to give it that "rubber" look. Remember to change the Subsurface Radius values to be equal so the subsurface color is not tinted red.
(Also, I know it's hard to see from the image, but I'm using Object texture coordinates )