Overloading your brush with paint and stencil shifting are the two most common mistakes. Fortunately there are simple remedies for avoiding and correcting both mistakes.
If paint begins to seep behind the stencil, you are using too much paint. Your stencil design will look blotchy or smudged. See image. If the seepage is minor, you can touch up the area with an artist's brush. If you notice the mistake right away, carefully wipe the paint off with a damp cloth. If the area is too difficult to correct with either of the above methods, simply paint over the mistake with background paint, allow to dry and continue stenciling. To avoid overloading your brush, simply swirl the brush onto a paper towel to remove excess paint. Gently touch the tips of the bristles onto the back of your hand to check for excess paint. If no paint can be seen on your hand, you are ready to stencil.
If the elements of your design appear to have ghost images, your stencil is shifting. See image. Correct the mistake using either of the methods described above. Stencil shifting is caused by improperly securing the stencil. If you are using masking tape and your stencil begins to shift, you should use larger pieces of masking tape or secure additional areas of the stencil. Spray adhesive is a fine alternative to masking tape. However, spray adhesive is more costly and clean up is more of a nuisance.