shop exhaust fan placement?

[hobby67stepside]

I first posted this on paint and body but there is so much more action here I'm going to ask again. My shop is about 40' x50' and 16' sidewalls. Fully insulated and lined with steel. I need an exhaust fan and wonder where I should place it - closer to ceiling or closer to floor. It will be close to a corner and I have windows on the opposite side I can open for air inflow. Does paint tend to move upward or drift down with gravity? What painting I have done in my shop seems to go everywhere throughout my whole shop!!!!!!!