I have done it to all of my Hi Point pistols, used Peformix Plasti Dip multi purpose aerosol spray rubber coating.
Put on about 7 coats on each grip. Make them good and wet when you spray them. They are soft and feel very nice. I posted some pics, but you really cant tell much by them. The difference is in the feel.
I also coated the Tapco front Hand grip on my saiga 12 because I like the feel so much.
Balance them on something to spray them, otherwise the spray will glue the grips to where the grip meets the over spray on the cardboard or whatever you put them on to spray.
It says to keep out of direct sunlight when doing it, but be forewarned, the fumes are horrible.
This is MUCH better than the spray auto undercoating that I had previously tried.
One of my pistols fell and hit on the grip on a sharp edge in the gun cabinet and it left a very noticeable mark and I thought well there goes that idea. After an hour, the mark had disappeared as the rubber retained its original shape.
I highly recommend it to those that do not want to put a store bought slip on grip on their pistol but want something that feels like an inner tube but looks better.