What I actually tried is, I installed a small $70 thermostat-run attic fan that pulled air from inside the attic out the vent screen at one end of the attic. It used the amount of electricity that an incandescent bulb would use, and cut my AC bill from $160 to $80 (in the summer). I installed it with a switch so I could de-power it 7 months a year.

Once, while I was in the attic, I learned a little about fluid air flow characteristics. The fan was on one end of the attic, and it drew air in from the soffet vents located around the entire edge of the attic, so only half the attic air was cool. By sheer dumb luck it was the half over the house, and not over the garage. If I had stayed, I would've added a second fan on the other end.

These attic evacuation fans can be run while the AC is running inside the house, thats why I chose it first instead of the whole house fan (which I may have added later).

Any windows that get hot, shade them on the outside (instead of just blinds or shutters inside). I honestly feel I got a good result for about 5 months a year by stapling loose weave cloth onto the eaves of the entire south wall, it hung down 3/4ths to the ground, and shaded the wall and windows. The cloth was stored in the garage the other 7 months.