Re: Single stage or Base/clear
Depends on your color choice. If it is a straight color (NO metallic) then go with PPG Concept single stage. Can't miss there. If you do go single, stick with PPG. There are others and they cost less. There is a reason they cost less and it is not just because of the brand name.
Anything with a metallic, go 2 stage. PPG's line of water base is one of the best and reasonable on cost for a water system. If it is something you are doing yourself and in a place that is not equipped to spray waterbase or has not done it yet, don't be a guinnea pig for the water system. It's not the same.
So for your orig. question, it depends on the color.