The section of exposed carbon in the middle of the joint is by design. This allows for repeated assembly/disassembly without the joint becoming loose over time. Once you have snugged the sections together, you will still see exposed carbon. Were this to be painted, it would not allow for as tight of a connection, and would diminish positive engagement over time. DO NOT SAND OR CUT THIS SECTION
If you have trouble breaking down the rod after use, use rubber gloves to get a stronger grip on the rod. Once freed, apply ferrule wax to the rod junctions to ease assembly and disassembly.