OK Zanji. i know this isnt required for ur combo but i am going to teach u the doton rasengan here.
I will also be teaching u the raiton one later on. We wont begin right away since im busy but u must first learn how to use ur Doton chakra. While i am gone u must make 250 shadow clones at a time and each must have a stone in their hand. They will try to insert their daiton chakra to make the stone crumble. like this, (inserts doton chakra into the stone in his hand and it crumbles away) Evry hour u must release ur clones and rest for an hour and then start again. When u have succesfully crumbled the stone come and tell me.