I did try and clean some cartos out and dry some out with a syringe, but it didn't work very well on that end.
Snow, I used a 20 gauge needle to clean the cartos. The smaller needle allowed me to go through the filler without damaging it, plunge the hot water/alcohol back and forth, and easily sucked all the water out when done. It might take a few syringes full of hot water/alcohol to clean it, but if you work with it you might find it to be quicker and effective. I'm sure your imagination can come up with an even better method that's quick and effective. The 18 gauge is something I just recently bought to refill with thicker juices. The size difference between 18 and 20 is pretty significant.