A simple way to clean oily skin is with soap and water. Several dermatologists suggest that using plain soap and water a few times a day is the cheapest and best way to clean oily skin (http://www.mothernature.com/library/bookshelf/books/47/102.cfm).
If you are not near water during the day, then you can use a pre-moistened pad that contains alcohol to help dissolve the skin's oil. Special absorbent face blotting papers also soak up the skin's extra oil.