I still have paint over the factory finish on most of the car, however there will be some sheet metal work and a small amount of filler needed. The car will go straight from body work to primer to paint fairly quickly, while being stored inside my dry garage.

I was planning on going with the PPG Omni system, I have a couple local autobody supply places that carry it. The omni MP182 2k urethane surfacer p-sheet indicates it is able to be applied over etch primed bare metal, scuffed oem finishes and body filler. "Sounds" like this would fit the bill perfectly for me, however I know the p-sheets are notorious for not vounteering the info about whether they are suitable to cover large areas of etch primed bare metal or large areas of oem finish. The two omni paints I was looking at, the MTK acrylic urethane single stage and the MBP acrylic urethane base coat both indicate they can be applied over the MP182. I just want to be sure I'm not taking an over-simplified idea out of what the p-sheets are saying.

Will a (mixed with reducer) gallon of single stage or base coat be enough or should I be buying enough to do 1.5-2 gallons(after mixing)? What about the surfacer if I wanted to be able to do 3-4 coats of surfacer?

Thanks all for the info so far.