I just got my shorty delrin drip tips yesterday, and I am loving it! I had trouble getting the filler out, too, but luckily I got one usable carto, and was able to try it. I think I need to find a slimmer needle nose pliers (if I have one). I might try Mutt's trick using the screwdriver from my eyeglasses repair kit.
Thanks for the tip about the filler being damp. That might help me, too.