As Ted says, freeze the parts, if possible warm the swinging arm as well, maybe stand it out in the sun (if it ever comes out that is).
Buy a long 10mm threaded stud bar, make sure it's longer than the swinging arm pivot tube AND the needle roller, thick washers and just pull the bearings into position, use a good fitting socket afterwards to sink them into the arm. Same trick with the rear bushes, they are easier to get in than out, if the stud bar is long enough you can pull them both in at the same time. . Protect your new paintwork from the washers by using some rubber etc underneath, something like a folded piece of inner tube.