This is either going to be super simple or super annoying, based solely on how Dagron's RNG behaves. He has a few aspects that can be manipulated, but there is an element of luck attached.
First, he always swoops in from alternating sides. Remember which side he's coming in from, because hugging the wrong wall or facing the wrong way can be a short ticket to reset town. Consider it turn-based - he swoops as his turn, you counterattack or prepare on yours.
Second, the basic gist of the fight is to dash into the blocks to make platforms appear, then use them to smack him in the head. He drops to the ground so you can spam away on him. When you drop the platforms, he'll assuredly destroy one immediately, then spend each of his next two turns targeting the other two. You need to get on one and wait for him.
You effectively only have one shot per set of platforms, as he goes back to his fire attack, which is harder to dodge, while you need to prepare to dash again. I chose to camp on whatever platform would be furthest away - it's much easier to jump into him and hit than away. Once you've gotten your attacks in, get to the opposite wall to dodge his next platform attack easily. From here, repeat that entire cycle. With maxed out Shampoo, Silky Cream, Super Pike Ball and Super Monster Milk, it will take two cycles to destroy him.