That'll be too thick.
Originally the paint is so light with a fine grain, the chrome almost shines thru it.
Giving a reflective effect in the sun. I would estimate the paint was orginally on a few mils thick.
I know this because mine were bought NOS back in the 80's.
Are these the fender gills?
I don't know what the louvers look like but from what you describe I agree with an air brush. The deal is that if it is so fine, almost like misting, you would need to have the paint to air ratio such that there is more air than paint and hold the air brush higher away from the the object painted to get the misting effect. May have to do this very slowly or else the paint will cake on. You do have to be careful on spattering but if you have a good air brush it should be ok.
You MIGHT be able to do the same thine with a rattle can but need to hold it above the louvers much higher, light 2 feet away, to get a misting effect. You have to move a little quickly, from one side to the other passing over the object you are painting, starting to the left or right of the object.
I do not have an air brush (actually I do, a cheapo one but never used it) but have read a little on air brushing.