One thing that really helped me with keeping the garage cool was insulating the garage door. I got a kit from Home Depot for a 16' wide door and it was easy to install and it made a huge difference. The other thing I did was getting 3' of blown in insulation above the garage.I built my house and 3 car garage about 14 years ago. Still haven’t finished out the inside of the garage. That’s another retirement project, after all the other projects. After a 34 mile ride in this 90 degree humidity factory today it will be a few months before I dig in too hard on anything, though.
Good luck with the projects.