No, I don't use any particular brand of MSM. I just buy the powder at the health food store, and mix it with her water. I started using it because a friend of mine uses it this way, and Emma walked around her house, one day, and drained all of the water bowls. She loves it! I just use about a teaspoon per gallon of water.
Emma doesn't eat a commercial food, so I don't know what kind of balance or unbalance that sort of thing would add to your dog's diet (now that mudpuppy mentions it....). I do know that plain gelatin won't hurt them, though. You can make meatballs with gelatin powder in them, and use them for treats. Em LOVES that!