Horribly painful blue balls. Am I close or doing something incorrectly?

I bought an Aneros Eupho Syn a couple days ago and have tried it twice now, following guidelines on the [Aneros Wiki](http://wiki.malegspot.com/index.php?title=Main_Page). Both times, I did ~20-30 minutes of flexing/releasing pelvic muscles before developing incredibly painful cases of blue balls and needed to resort to traditional penile stimulation for relief. Even then, I’m left hurting for 30-60 minutes post orgasm before the pain fully subsides.

Am I doing something wrong? The Aneros certainly feels good, but owww…