How are you getting water into your bearings? I'd resolve that and then not worry about how to get water out of bearings. But I think you guys may be on opposite ends of the extreme. The bearings are sealed, and while WD40 has mild penetrating characteristics, it's likely that it's still not penetrating the seal and breaking down or displacing the grease. I'm assuming your doing a spray on/wife off action - not trying to stick the red straw directly into the seal/face of the bearing and spraying wildly.

Conversely, if some WD40 can get in, it can bring dirt with it. So make sure you clean your bearings before you clean your bearings. You know, just like using the dishwasher