Hulk ascension strategy

Hi, all. This is my 3* Hulk situation. At this moment he is my 3* favorited character, so that I can grow the 3* and merge him with the other 266 lvl 3* Hulk. But after that, what should I do with the 3 4* Hulks? What is the best strategy here?

Thank you:)

Hi, all. This is my 3* Hulk situation. At this moment he is my 3* favorited character, so that I can grow the 3* and merge him with the other 266 lvl 3* Hulk. But after that, what should I do with the 3 4* Hulks? What is the best strategy here?

Thank you:)