the 217 can be used for concealer, or for shadow (for either applying shadow softly, or for buffing colour out). for either of these uses, you should always use the tip of the brush, not the sides. by using the sides of the brush, you have less control of how the product is applied.
as for the 109, when applying product as a highlight, use a windshield wiper motion. if using it for cream or liquid foundation, buff the product on with a circular motion.