Ive done this dozens of times on all sorts of cases. Stuff some paper down in to the crank then melt some paraffin wax in a double boiler, pore the melted wax over the paper and there you have it, perfectly sealed. after your done dremeling, wipe out the shavings with a oily rag and hit the wax with a torch for a few seconds, the wax plug will fall out and after you remove the paper you have a perfectly clean case. you don't have to worry a bout any left over wax because its petroleum based and will simply act as a lubricant if any is left behind.