In recent years, oatmeal products have become a preferred choice for acne as well as an ingredient to make homemade exfoliant for oily skin. What you do is buy colloidal oatmeal, grind it into fine powder, and dissolve it in lukewarm water. When a paste like consistency forms, apply it on your skin as a mask. Use circular motion to massage the skin gently.
Keep the mask for 15-20 minutes and wash off with clean towel.
Another option is to prepare oatmeal as you would usually do for consumption, let it cool a bit and then apply as mask on your skin. When the surface becomes little crusty, remove the mask, wash your face with lukewarm water and pat dry. Use either of the two several times a week. This mask will simply absorb all the extra oil on the face.