Adding More Cob After Finish Coat

Hi, just wondering if anyone can tell me if it is ok to add more cob to a rocket mass heater after aftera finishing coat of, say, olive oil soap or other product has been used? We want to do a finishing coat now, in order to keep the dust down for the winter, but may wish to come back to it next summer and add some detailing. Feedback would be appreciated, thanks. :O)

My feeling would be that you would want to scratch off the coated surface layer where you want to add cob, at that time. If you have a smooth finished surface, you would want to significantly roughen it anyway so the new cob would bind to the old, regardless of treatment.

Oh thanks, Glenn, that actually makes so much sense.