Stippling brushes are quite versatile, can be used to apply both liquid and powdered products, and are used for when you want a sheer, natural look. This means that only a thin amount of product is needed when applying, and it is easily buildable. Also, keep in mind that the product only needs to be applied onto the white bristle section of the brush, as these bristles are really what brings the look together.
If using liquid products:
Squeeze a dime sized amount onto the back of your non-dominant hand and then gently dab the foundation with the brush to pick up the product. Make sure that the white bristles that are picking up product, as they are what will bring the look together.
Lightly begin patting the brush with the foundation onto your skin, tapping on the face over and over again overlapping taps. This is called "stippling." Do NOT apply by buffing in the product as some suggest in technique videos, that is for flat top kabuki brushes.
Lastly, swirl the brush gently onto the skin to blend everything together. The most important part about this is to make sure that only the white sections of the bristles are moving when blending, so this means use a very light touch.
If using powdered products:
Swirl a small amount of powder onto the white section of the bristles and tap off the excess.
Lightly sweep the powder onto your skin. If you have concealer on, you may want to pat those areas first before sweeping the powder on.