Anyone know how to get through this room? I used to know but forgot.

I know you have to leave as much earth as possible to avoid having it all blocked by boulders. I know you have to use the second lever from the left down below to get the right amount of earth to tunnel through to get to the exit. I know you need three bombs to get to the exit. My problems:
1. What path do you take to get the bombs you need?
2. In what order do you get the bombs to have the 3 you need?
3. What path do you take to get to the second lever from the left?