
The separation I spoke about is all indoors - however I have had to put a lot of work in to Willow's play on walks as well, as she would bagder Linc constantly if left to her own devices.
The first thing I did was work on improving her response to me in his presence - for that she had to be on lead. Nothing special, just keeping her on, rewarding her when she looked at me, and if she was trying to pull to get to him I just didn't go anywhere - if she persisted I turned around and walked further away from him. Now, don't have an image in your head of her walking away with me - she was not happy about it lol! A lot of it was me walking a puppy backwards :-P But the message did sink in when it was happening every time she ignored me and tried to run after him. It's helped her lead walking a lot too.
With better response but still on lead, I started to reward her for turning away from him while she was with him, or for walking with him but not starting to badger him. I carried that on off lead.
Right now we're at the stage of 'away', 'leave' and rewarding her for choosing not to annoy him. 'Away' I use for if she's already started to do it - again this was started on lead so I could enforce it. 'Leave' I use when she's about to start on him and with those combined, I'm getting more and more opportunities to reward her when she's chosen not to do it in the first place.
For general play if it gets OTT on walks then recall is your best friend - but the key is not to just reward her for coming back, but to then build up the duration of staying with you. Again it needs working when she's not being OTT to start with, to give her a better chance of success. So rather than just recall then a treat, you'd do that the first time, then recall + stay a second (not a formal stay, just paying attention to you) then a treat, then stay a couple of seconds and so on. I do this randomly on walks as well with Willow and it's been very useful in getting her less distracted.
The idea as always is to avoid the really bad stuff happening to start with so if you can build up the behaviours you want in less trying situations (so when she's just socialising or mooching about but not playing like a demon to start with), then you've got a much better chance of getting them when you need them; and if you can start with her on a lead then you won't find yourself in the position of having to restrain her, but rather you can manage things so they don't reach the level of intensity where she's losing control of her teeth again.