A setting powder should be used after contour to hold the look in place. Without this, contour can start to smudge as the day goes on. However, if using a powder contour, you may prefer to apply the setting powder before the contour.
When using a cream contour, a dusting of translucent powder is applied afterwards to set everything throughout the day. A translucent powder shouldn’t show up at all, although some powders are lightly tinted.
Powders can be pressed into place or dusted. If pressing on a setting powder in order to ‘bake’ foundation or concealer, then be careful around contour. Baking is when powder is applied in a heavy layer, left to set (or bake) and the excess brushed away. Baking keeps makeup crease free for longer. It can be used to correct a contour, but baking directly on top of the contour will diminish the effect.
If using a powder contour, you may prefer to use a setting powder beforehand. The dry base is good for the dry powder to stick to. However, a light powder application on top of a powder contour can give it staying power.
There are no hard and fast rules to make up, the trick is to find what works for you. Some prefer to apply setting powder before contour, and set with a finishing spray. It will depend on the contour you use, the powder you use, and your skin type.