I usually remove the shaft and chain between 2 trees with a comealong.. soak it good thru both ends with penetrating oil or atf mixed with a solvent of choice ( kerosene, deisel, mineral spirits ).. and then get a punch, and try to tap on the leading edge of the outter sleave ( slide back the plastic covers ). Once you get it moving by tapping, retensio and keep going.. once it breaks free, slide them apart, and sand smooth the inner shaft, and then i like to wad up some metal pot scrubbies and then wet down an old rag with oil, shove it in the tube, and then the pot scrubbie, and then force it thru a few times with a rod. Then pour some oil down the ID, or shoot a few shots of grease in there, then grease up the inner shaft and slid ethem back together.. should be good to go.
On some of my shafts there is a grease zerk on the outside of the outter shaft, and a coresponding hole inthe plastic sheath.. line em up and lets you grease to the inside of the shaft periodically.
if you can.. chain them up so you aren't pulling thru the u-joint.. etc..