I like to use a combination of fine and medium grit nonskid. Awl Grip sells them by the can, Inturlux also sells a similar product.
I pour them into my spray gun dry, just the nonskid. Then open the tip just like you would to get more
paint, then adjust the fan. Spray them about three feet above your
work moving the gun from side to side.
This has given the most even and most professional looking nonskid I have seen.