Wrap each potato securely in heavy-duty aluminum foil. Place around grey coals on bottom of grill. Cook 1 hour and 15 minutes or until potatoes yield slightly to pressure. Turn potatoes every 20 minutes, using hot pads or tongs.
Unwrap potatoes, and cut a slit in top of each. Press sides to loosen inside of potato. Add butter or sour cream and seasonings to taste. Serve hot.