Dirty shotgun hulls
Falconeer--Re dirty shotgun hulls: If it's dirty enough you have a though about not reloading it, toss it.
Shotgun hulls are easily available at almost any trap range; you can normally pick up for free more than you could reload. If your club has rules about that, go to any public trap range and scrounge hulls there.
We clean rifle and pistol brass because the crud on the brass might scratch the dies. The plastic part of the shotgun hull is much softer, and the brass part is much thinner than rifle or pistol brass, so there is much less pressure on the shotshell reloader resizer, therefore less wear and tear.
I've never heard of anyone cleaning a shotshell before reloading.