I did it the first time with needle nose pliers myself. But if the last person put the sleeve nut on especially tight then good luck with the pliers option.
I finally made up my own wrech to do the job from an old bit of bicycle frame tubing that fit like a glove and a cross pin that was carefully filed down to fit.
If you're handy with tools a scrap of 1/8 steel plate could be cut and filed to fit between the slots and grabbed with a pair of vise grips to do the job.