Going to paint some metal decking? I am going to paint some decking that is around 16ft high. There is around 7,000 sqft and i will coat it twice since it is already painted grey.. The ceiling is in good condition so i will probly air clean the dust off it. I am going to say the material cost is $15 a gallon with coverage of 175sqft. So 7,000/175=40x15= $600 per coat.. Iwill be using roll scafold and i am sure i can spray this in two days.. What would be the average rate persqft to spray this by a commercial standard? Thank you for the replies