Clean the pump out after each use by pumping clean water through it and into a bucket. Then fill the bazooka with clean water, as if pumping mud into it. When full of water, lay bazooka horizontal over a bucket and rewind the cable back up, which pulls the plunger and all water back up the tube. Do this a couple of times and the inside of the bazooka will be clean and ready to put away.
Replace the cable with a new cable. Easy Peasy. If you really have a flipping nudo adentro, you may have to remove the cable barrel to gat at the cable. Hopefully not.