As MSO said....go easy. If you don’t ream enough, no sweat, do it again, but you cannot put briar back. If you are going to keep a cake, determine the thickness you want before you begin to ream. Go slow and try to keep the reamer centered so that your cake will be even. I and several others, do not keep any cake in our pipes and simply wipe out the bowl with a paper towel after each smoke as mentioned above. Good luck.
P.S. I have found the PipNet reamers the easiest to use, as I sometimes need them to clean up estates.