They also have a specific tool for threading nipples in deep rims - it holds the nipple until the spoke gets up to a certain point then it lets go.

I have one but forgot where I got it.

However, after using that, a spoke (thread nipple onto it, line up nipple with the actual spoke, use spoke wrench to pass nipple to actual spoke), and some other things to build a myriad of Zipp wheels (perhaps total 20-30 wheels), I found myself going to the spoke most often. Always have a bunch around, you can verify that the nipple you picked up wasn't a random incorrect size nipple (1.8 mm vs 2.0 mm) before you get it in the rim and threaded onto the spoke.

When I unlaced Zipps I'd do the same but in reverse - unscrew the nipple a bit then allow it to thread onto a second spoke I'm holding. Then I pull it out like the game Operation.

For getting rid of the 3 nipples in there, the sticky thing idea works. I'd use a spoke, maybe dab some grease on it (sticky) or tire glue (stickier) and go after those SOBs.

good luck,
cdr