It works brilliantly! After 2 tubes of canesten for me and 2 bottles of nystatin for DD with no let up we got daktarin, the thrush was gone in a week!
I used it morning and night. I'd put it on after morning feed, and then after her bedtime feed. You should only need to wash it off if you can visibly see some of the cream still on your nipple at the next feed, otherwise I was told there was no need to wash my nipple before feeding.
One thing I will say, make sure you continue using it for at least 5-7 days after the thrush has gone to prevent it from coming back straight away.