The flush was what I was talking about earlier, except my vet called it "infusion". Having it done one time didn't seem to do the trick with mine. It took 3 days in a row and I think it was about $30 a pop. They have to be in heat when you do it so the cervix will be open, otherwise you can damage the cervix and they'll never carry another foal again.
No - this is different than an infusion. They use chemicals that clean off the uterine walls. It stays in overnight and then is rinsed out the next day. It requires the mare stay overnight with the vet.