Faux can only be used as an adjective meaning fake:
The faux-marble finish
Don’t use faux as a verb. He didn’t faux-finish (pretend to) the walls; he really did finish them. Also, avoid faux finish as a noun.
Avoid using faux to describe paint techniques such as color-washing, sponge-painting, and rag-rolling. These are real finishes. Faux can only describe the effect or thing you are imitating: faux marble, faux wood, or with a trompe loeil window, the faux window. If you do not know the finish used, decorative finish is acceptable. Also, use decorative painter or decorative artist rather than faux artist.