Cindy Lietz, the polymer clay tutor, provided a video that showed me how to use Micromesh abrasives for sanding and polishing polymer clay projects. These are great and come in 9 grades of coarseness. You can even purchase little polishing swabs for those hard to reach corners.
Here is what the micromesh squares look like, and believe me, you will be "wanting" to sand and polish your projects. Just google the word micromesh and your city for a local provider. Or, you can find suppliers online. Click on Micromesh above for a preview of her video using this product.