It depends on the vintage of your Blackhawk.
Old models and new model alloy grip frames up to about 10 years ago were anodized. Since then they are powder coated. The powder coat strips easier and products like Klean-Strip will work. And may take the black of of anodized grip frames, but I haven't tried it.
If your gun is about 10 years old or older the grip is anodized and oven cleaner is the ticket.
Stripping, Polishing and refinishing alum alloy frames:
To remove all the old black finish, Easy Off oven cleaner works best. You have to buy the "dangerous" oven cleaner, the kind with lye. Don't settle for the fume/odor free kind, it doesn't work. You can cleanup with 800 grit paper. But you don't want to go thru the anodizing, just get the black off. The aluminum is very soft under the anodized layer which is similar to case hardening, and will dent and scratch easily.
For final polish preparation, use 1000 grit. Then 2000 grit paper and bring to a shine with a well used piece of 2000 grit paper.