Dry Bowser's attacks:

Fire spew - Dry Bowser will shoot up to 5 rounds of flames at you. The flame at the front deals the most damage of 4 and the flame at the back will deal the least damage of 2.

Bone throw - Dry Bowser throws a bunch of bones at you in no particular pattern. If the bone is rotating forwards, it will roll upon landing. If it's rotating backwards, it will jump over you and roll to the right to try getting a sneaky hit in.

Shell spin - Dry Bowser enters his shell and attempts to bash into you. When he moves backwards, there's a chance he'll drop one of his limbs or head which you'll have to jump over. If you stomp on his head, the attack will end quicker than usual.

Fire rain - Dry Bowser jumps towards the background and dives into the lava, shooting fire everywhere when he rises back up. You can move left and right to avoid the fire falling down onto the arena. You can't stay still forever, as some of the flames will target Waluigi's location.

Chase sequence - Dry Bowser will start charging towards Waluigi which will start a chase sequence. You have to jump over his flames while stomping on Pumpkin Goombas to try to trip him so that the sequence can end.