Can you help me clean the old stock heatsink foil off my heatsink?

i have something better then the stock heatsink stuff. and i was wondering if i could just hydrogen peroxide to clean it off. no i dont have any rubbing alcohol. so please help me with the peroxide. if i can use it or not. if so how much of it. should i mix it with baking soda if so how much of each. i only need a tiny little bit to clean off the old.