Pitbull "nipping" tips/training

When raising my first pit bull puppy I made it a priority to teach him NOT to bite. Even when wrestling, playing tug, "boxing," etc - he will show his teeth, but will never close his mouth on a person...even when we give him bones as a treat he's very tentative at first taking them. Just last week we rescued a 2nd pit bull, however she bites when she plays. Both pit bulls are 1 year and he will not bite her when they're wrestling, but due to her nipping at him (playfully), my male pit bull now has scratches and scars all on his cheeks. Slowly but surely they are learning "Settle Down," but does anyone have any tips or advice on how to get her to quit biting during play?



I don't want them to get confused and think playing is bad - but perhaps playing too rough is...



Thanks in advance!

Pitbull "nipping" tips/training