"Underspray" is the undesirable spray that finds its way underneath stencils and into areas where it is not supposed to go. Adhesive stencils are great for clinging to surfaces to avoid such issues, but highly contoured locations can still present challenges. One thing you can do is use a hair dryer or heat gun (use on low and be cautious as it works fast) to warm up and loosen the vinyl once its applied. This makes the stencils a lot more pliable and allows you to really set them into the high contoured locations. An old credit card, hotel room key, or similar type device is also a great tool for pressing the stencils tight in tough to reach positions.