You can add the cows milk to the already made up bottle of formula, just be aware that it may cool the bottle down if you’re adding it in cold. I actually found that my wee girl didn’t like her bottle with formula and cows milk together so we went for a straight swap onto cows milk but she won’t take it cold so I have to warm it up🤣x
Today I’ve done say 4oz boiling + 4 scoops + 4oz cows milk (cold). She’s loving them 😂