Rattle cans are not really the right way to do that job. I am appalled that the things big-box stores will sell you with a straight face, they stock many things that are wrong, require specialty skills or are downright illegal, and all the burden on you is to know the craft and know what to buy, and then their $8/hour clerks advise you wrong (because they don't know)! I prefer to deal with specialty suppliers. It doesn't take a half hour to visit their shop, and their prices are often better too. My locksmith warned me 3 times that Code requires lever handles in commercial spaces, not door knobs. Bless him!
OK so you're committed.
For a mask? I would use a couple of manila folders. Readily available, cheap, and abundant since many people are switching to hanging folders. However expect to waste 70% of your paint and it'll look amateurish. It will also be impractical to paint in any wind.
They also make apparatus specifically to spray pavement lines, but that will require rattle-cans which are compatible with it.
I would also consider a roller and canned paint. It's far cheaper, and you'll waste less than 10% of the paint. Rollers proper come in 3" and 4" stock widths. Some rollers let you "hang a little off the end". Roller covers (the part that absorbs the paint) can be cut down to any needed width, bonus points if you work it so the leftovers are useful. This too runs the risk of looking amateurish unless you have a steady hand. Consider "snapping a line" with a chalk line.