Quote Originally Posted by encorehunter View Post
A portable swamp cooler can go a long way to making it more comfortable for a relatively low price.
My suggestion as well.

I worked in a shop for a couple years that was miserably hot. The owner was a cheap, thief piece of garbage so he didn't care. I bought one of the big rollaround swamp coolers out of my own pocket and it made a huge difference.

If you buy or borrow a thermal camera, it will show you where the hotspots are.

I doubt there's any insulation in the attic or walls since the garage is not an occupied space. You are likely getting a lot of heat transfer from the roof and exterior walls so a vent or probably won't help much.