Bidding a commercial job. Theres about 55,000 sqft of ceiling I need to spray. one section is corrugated steel. While the other is almost a type of gypsum board. There are alot of steel rafters in both sections. And the ceilings are very greasy from all the diesel machines that were running in there(metal perforating plant I believe). Ive never had a Job this badly greased. The ceilings are about 32ft high. Thought about blowing off any loose debris or dust that might be up on the rafters and just spraying over with an modified epoxy or a oil based dryfall. The gypsum board ceiling is all brown from exhaust fumes, but I do believe anything I spray will soak into it and adhere. What is typcial sqftage I would get from a gallon when there are alot of Rafters + Corrugated roof. Also what do most of you charge per sqft for this labor/material? and what to do about the grease??? would an epoxy or oil based adhere and last long on it??I am thinking of test spraying both sections to do an adhesion test. Thank you for all your Help.