This method will work best on cards with a brayered background since it is much harder to avoid the halo effect with a brayered background. Halos don't tend to be as much of a problem if you are just stamping over portions of other stamps. I don't like the idea of having extra layers to a card with stickers, so I tend to stick to using masks. Masks can be reused. I keep my masks filed away for future cards.
Reverse masks are great of limiting the image of one stamp to stay within the boundaries of another.
I used the reverse masks for my Royal Treatment card to make it easy to color with chalks and still get a hard edge. Spritz the back of the stamp lightly with water from the spritzer bottle. Wait a second so that the water and ink have a chance to run together a bit. Stamp lightly on your card. The second stamped image will be lighter than the first.