Wall O' Text incoming...
As a hobby I restore straight razors now and then. I have worked with SS before and it can be cleaned up. there is buffing compound out there for harder metals you can use. if the scratches are too deep for simply buffing you can get auto sand paper, lubricate the paper with something like WD40 and sand out the scratches. At least this is how you would restore an SR blade, I see no reason why an ss mod would be different. (Obviously you would want to remove any batteries before doing any work on a mod).
For larger surfaces, buffing with a dremel can give an uneven appearance, I would suggest an actual buffing wheel on a grinder, for smaller surfaces a dremel should be fine. When using a buffing grinder, put up a drop cloth behind the grinder, in case the wheel fibers snatch the mod from your hand and throw it, the drop cloth should catch it and hopefully prevent more scratches. If using a dremel, make sure you use a piece of cloth to protect your mod from any vise/clamp teeth when you secure it for buffing.
If you need to go to sandpaper for deeper scratches you are going to have figure out the grit to start at, then work your way up to 2k grit before going to buffing. For simple tool marks I would start at 800 grit and step up or down based on the results, then work up through the grits to 2k, then move into buffing. I sometimes add an extra step with softer metal of using a turtle wax compound but I doubt you would see much good on something as hard as SS with this step. I suppose I could have skipped even mentioning this bit, but I promised a wall of text and it was looking a bit thin.
After buffing if you want it to really shine you could try a polishing compound like MAAS (I have MAAS with a lavender smell, works great and is pleasant to work with).
If you are going for a matt finish you could stop at 1-2k grit sand paper and not buff or polish at all.
If you need more info on this you could check a Straight Razor restoration forum and maybe get some helpful tips there, those guys work with all types of material and the metal they work on is razor thin, and very delicate in some areas.
hope that was helpful. ...cheers
/wall