We can work on gels stained in many ways, including commassie blue-based staining (traditional commassie blue, Colloidal blue, and SimplyBlue, etc.), fluorescent dye staining (such as Molecular Probes' SYPRO Ruby staining), and sliver staining.
For silver staining, we have found that a lot of commercially available kits work quite well, such as PIERCE Silver SNAP, Invitrogen silver stain, and Bio-Rad Dodeca Silver Stain. Be sure to check the product brochure or call their technical support to make sure that the silver stain method you use is mass spec compatible. Develop the staining to the minimum in order to maximize the chance of identification by mass spec.
All gels, no matter what stain you use, have to be fixed. This step is generally included in the protocol or combined with staining steps in most commercially available kits and methods. For some staining procedures, such as Zn stain, no fixation step is included. In that case, once the band is cut, it should be fixed in the tube with 10% acetic acid and 40% ethanol for 1 hour.