If you use it properly the 3oz. will do a car several times. If you put the entire 3oz on in one application you are goo g to have heII getting it off.
Depending how far the overspray had to travel to your hood and how well waxed the hood was clay may remove it just fine. If the clay doesn't get it all we need to know what kind of car/paint you have to determine a good next step.
My wife sprayed polyurethane on some piece of furniture in the garage and the overspray settled all over her Explorer. When I found it the paint felt like sandpaper. I was able to successfully remove it with Mothers clay. So I would think it would depend on what kind of overspray you have and...
Not the way I use it. I have cleaned overspray off of my cars several times with it with no obvious ill effects. I had a 1998 Ford Explorer that had heavy polyurethane overspray on it from a careless furniture refinishing job (mine) that felt like sandpaper. A careful wipedown with lacquer...
I am not familiar with Lanka but I have used Dr. Color Chip and found I could do the same thing with what ever touch up paint that matches and lacquer thinner. For me the end result was pretty much the same and Dr Color Chip cost way more. Just use old "T" shirt material, a plastic card (old...