We tried once (our stud was too young) with a stud from a breeder... we had to leave Rosie over with the breeder that time, and though the breeder was experienced and the stud proven, and we were told they tied 3 times... it didn't take.
So, 6 months later we bred her with our boy.... Rosie was always the dominant female with him, but things went well and we had pups... but Rosie would do the hump him back thing too.. even after they had tied already. Its a dominance thing, a lot of the time, for the female... She is saying, "Ok, there is a reason I let you hump me, but you're still not the alpha here".
Im sure the breeder you mentioned wouldn't mind if you give them a call and let them know your situation, that you're trying and you'd like to have another option if it doesen't work. Many are very kind and understanding in this regard, so why not give them a call for a bit of a heads up, and reassurance for yourself? The advice you have gotten here sounds like the way to go, very knowledgeable... but just to say how we let things happen with our dogs... whenever we were home during the days Rosie was in the 'window', they were left out together in the house. Our male, Dundee, underdog that he was, seemed to need that time out with her to 'get in the swing of things' and get really into chasing her. It was always a chase.. and she would growl at him, and snap, even when she was flagging. We had to be very firm with no attention given to either, no holding or petting, so they would actually concentrate on one another. After a time, poor Rosie would often run to us looking for protection from him, and I remember feeling horrible, but we had to make her stay down. If you want puppies, its what you have to do, or so we told ourselves.
I am a little concerned with the issue of Brutus being on the chain... I understand you have very good reasons and need to keep him safe... but if hes not free to chase her, it makes it difficult for the mating to happen. A first timer female, let alone most females, isen't likely to just come over to him on her own when shes ready. He really needs to be able to chase her around and not have areas where she can get away from him. Do you have a room in your house you feel comfortable leaving them out together in? I think each session with them together should give them at least 4 or 6 hours to flirt and chase before you expect anything to happen. It really sounds like he has never bred before, so I think he needs the time to figure the whole thing out. And, ignoring them both while they are together, and only keeping watch out of the corner of your eye, is what we were advised to do.
Im thanking God for Annie & Brutus puppies!!