I recently started cleaning my brass with the stainless pin method and started having this same problem. I would get brass galling from the inside of the case to the powder funnel after 30-40 rounds. It would end up taking a lot of effort to pull the case off the funnel. At first I would just polish the brass off with a Dremmel , this did not last long as I was not interested doing this every 50 rounds. I found a post somewhere on the internet where a Dillon rep mentioned that this is common on new cases and that there was no real fix. According to Dillon the slight amount of carbon left on a fired case from normal case cleaning methods acts as a lubricant for the powder funnel.
What has worked for me is to take my vibrating tumbler with some corn cob media and add a cap full of liquid car wax to it; I tumble the cleaned cases for about 10-15 minutes and then load them up. I have not cleaned the powder funnel for several thousand rounds now. As a side benefit the cases go through the sizing die very smoothly almost as good as if they have case lube on them. Every so often I add a little more wax to the cob media, but I have not needed to change the cob media yet since the brass is all ready clean and it has so little run time on it.
You mention you are using twice fired brass. If you do not get every last bit of brass off the powder funnel it will start to build up again in a very short time, using wet sand paper like mentioned should do the trick.