I've lost the balls once in my RM1610 screw ... I made a rod the right diameter (pitch diameter minus diameter of balls, though it's not critical) and just stuck a big magnet on the side of it. That makes all the balls just stick in place easily without grease or anything.

The magnet I had was a spare from my wind turbine (2"x1"x0.5" neodymium) so extremely strong ... but you could probably do it with less.