Wand on top of cage, bit of ball squeezing. It surprised me the first time just how easy it was!
She removes the wand when I get close, then it just spills out gently. Wand back on almost immediately and repeat.
After 3 weeks denied the first one arrives very quickly (about 2-3 mins) second one about the same then maybe a little bit longer for the third. When we first started our chastity journey she could extract a fourth, but she decided that extra one could take me out of the zone so she now has a 3 spill limit.
I actually find them incredibly satisfying, the good sensations last so much longer than a simple wank & explode. Then again it's getting to the point where I don't actually remember traditional orgasms any more!