TheNewGuy says...

How about actively removing the heat: a gable-mounted exhaust fan, with
or without a thermostat control. Depending on the CFM, you'll need a
certain area of "inlet" into your shop of fresh air - got a screened
window?

The collateral benefit to the exhaust fan is it moves out the fine dust
too.

-Chris

A gable fan and vent system would be nice, but it is a cinder block
building and the cinder blocks go all the way to the crown. Would a fan
really cut down much on the radiant heat?