Ryan, If you are talking about an exterior plaster, I would try a lime-sand plaster applied to the cob...You might want to read the chapter in my book, however, so you can learn as much as possible about lime-sand plasters. They can be tricky and require a lot of knowledge. Good luck.
They gave me pumpkin ice cream. It was not pumpkin pie ice cream. Wiping my tongue on this tiny ad:
Permaculture Voices 1, 2 and 3 - all 117 hours of video!