I honestly see no point in it. It's probably best to just barrel it as is. The campden tablets are good for fighting infections but in this case it's not necessary. As long as you cleaned it out thoroughly using hot water several times you should be fine. What's the worst that could happen? When using a barrel, it's trial and error more than anything.
Whiskey Barrel: Russian Imperial Stout
Bottled:Amber Ale, Bitter Chocolate Oatmeal Stout
Drank/Gone: Red Ale