I'd say a thin layer over your face, that's what I did when I was on the regimen and my marks seemed to fade quite alot. If you place it on each one it will take you ages! And might not have the same effect of overall skin tone evening. Where spot treatment may be of benefit is if you see a new spot developing: Dan says if you put AHA on it as soon as possible it can help stop it from developing. From my experience I'm not sure if it works but it might help a bit.