firstly i'd recommend rcs liquid mask (
)
Presuming the grey is streaked, although it looks like it's just the streaks from the markers you used.. the only slightly tricky thing i could see when using cans would be the streaks in the grey. couple thoughts(although i have never used cans so don't know if it is possible or would work) would be to attatch a straw to the can to get a finer line or use a shield made of card or scrap lexan or similar to spray against to get lines. closer you hold the sheild to the surface the tighter the lines would be. another idea would be to take a sheet of card and cut a very thin long rectangle in it to spray through. strips of tape or wire could work to a certain degree.
none (i don't think) would produce the type of streak effect you would get from an airbrush.
go have a play/experiment on some paper and see what you can come up with.