Is it possible to silver stain after Coomassie?

Yes, it is possible to silver stain after Coomassie but it is not ideal. This is because the silver stain reacts with Coomassie resulting in a high background. The background will be especially high if the gel is not de-stained properly. Taking care to de-stain the gel thoroughly will improve the results. However, patterns are most crisp and clear in gels that are not Coomassie-stained.