To clean/fill them, you need some plyers to grip the ring from the spike and rip it out, it takes some force and is a little dangerous. When the ring is out, the spike just twists and pulls out. You can then clean and fill, then pressurise. You will probably need a shut off valve (impossible to find) for pressurising through a coupler. When you are done, just put the spike and ring back in the same order.
Its pretty much a matter of getting used to it, with practice, the're just as easy as post mix to use.
Good luck