Old-ish thread, but since I just did a Hatta BB......
The balls are actually held in place by a thin black plastic ring outboard of the balls- you can see it in the OP's close-up photo. Using a screw driver you can pop the balls out- basically you just need to overcome the resistance of the plastic ring. Each ball gets easier to do, then the last few will just fall out (as will the plastic ring). Q-tips and paper towels and you can clean out the cups. To reassemble I stuck a finger up into the cup, put the plastic ring on my finger and started putting fresh bearings in, using my finger to move the plastic ring around to create clearance to get the balls in. As more balls go in, the ring starts to get held in place and the last couple of balls require a little bit of pressure to get past the plastic ring and into position. I reassembled each side dry and then packed with grease once they were all together. I think one might have a hard time getting things back together if the cups were greased in advance and everything is slippery.