We recommend to clean your luggage by using Windex (or any other glass cleaner without Ammonia) or Dawn Dishwashing liquid with degreaser (or similar product) on a non-scratch dishwashing sponge. Do not use products with petroleum or ammonia as they will damage the finish of your case. With a little effort and perseverance, most of the scuff marks should come out.
Another product we recommend is an industrial cleaner called Loctite ODC cleaner (20162) ($12 - $15/can). It has a strong smell, but this is what they used to clean the product at the factory. You can find a dealer in your areas by clicking this link. Note: This product works better than any of the commercial products described above, but it will still require some effort to take marks off.
Note: It is normal for all luggage (whether polycarbonate or ballistic nylon) to get dirty and show wear and tear from use. If scratching and scuffing pose problems for you, we recommend the TITAN® 360º Four Diamond Edition (NEW!). The Diamond Collection has all of the features that made TITAN® luggage famous worldwide, with the addition of an attractive diamond-pattern exterior that looks great and is virtually scratch proof.