Not enough, or too much

So I decided out of simplicity to use duplicator primer. Lets let that be a given?.

How far should a can go? It is a 12 oz can (including propellant).

Also though, is there such a thing as making it so thin that it is actually worse than the original aluminum? Thin enough to etch and promote corrosion without the added protection of the pigment and TiO2 on top?

If I do two passes to make a more color than base metal job it seems good, but the cans don't go super far. I don't mind the expense, just curious if too little is worse than none at all. I might be adding a few pounds to my empennage in this process.

On the skins I decided to just do the rivet lines, more or less. The thin sheet will show corrosion easily enough but will be painted exteriorly.

Duplicolor recommends 2 to 3 thin coats to achieve a uniform coverage with their self-etching primer on bare metal. This is gonna be pretty much the same with any of the spray primers. Its just too hard to get a decent coverage with only 1 coat. If you're leaving "holidays" on your primer coat, you might as well not prime at all. Probably not any worse, unless you've scuffed all the Alclad off.

If you're looking for the thinnest, almost translucent primer coat, I'd go with the zinc phosphate primer. The yellow can be applied really thin. Still at least 2 coats though, probably not any more economical in the long run.