Buckfever,
RCBS used to make a small wire brush just to fit primer pockets, I used one for years but I don't know if they still make them. What I use now is a primer pocket uniformer in a power screwdriver. Since the bottom edge of the pockets is the only part that needs to be clean the uniformer does only the minimum that's needed. When they say the brass flows under pressure that includes the head of the case to a small degree. So using a uniformer keeps them clean and true at the same time. This process needs to be powered or it will get tedious quickly.