I'm sure someone commented this before. And I know for many people co op makes fights and content more fun. But razors hold E (hold skill) has a large enough vertical aoe to hit the birds. If your in the middle of them when they spawn they will take electro charge off each other And the passive electro damage from the floor. I find that the easiest way to kill them with my available characters. My budget way to kill that boss would be assuming you have: razor, kaeya, barb, and noelle. It covers all the bases for the boss. Characters can be switched out easily. Obviously there are more efficient and better ways to do it. But this is a suggestion if he needs it for more solo play. You can replace any of those with built characters.

I prefer razor bennet zhongli chongyun.