It really depends on the type of material the touch screen is composed of (Glass, Acrylic, Gorilla Glass). I would suggest using a buffing agent that is specific to your type of device screen as to not damage it any further. These guys have it broken down by screen type so you might look into what they have or something similar from another manufacturer.
[http://www.tdillctechnology.com/store.html?limit=36|TDI-LLC Technology - Glass, Acrylic, Gorilla Glass Compounds]
Hope this helps.