The puncture pin section of the bucket changer comes out with a 3/8" allen wrench. That's the part that screws into the ASA.
The actual puncture pin and seal is removed with a tool that looks like a flat screw driver that has a notch in the center to clear the pin but still bite the cup where the two cut outs are. Then it will unscrew counter clockwise. You can make one from a flat screw driver that is wide enough to reach those notches. A regular flat head screw driver can work, if you can grab just one or the other notch and "pivot" on the pin, but don't use a lot of force or you can mess it up.
Clear as mud?

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