when i foster adult pits i have 3 adult dogs- rottie , GSD, pit mix. i keep them totally separated for a week and just let them get used to the smell of the new foster here. after a week, i allow one dog to walk past the fosters crate on leash so the foster and the resident dog meet seeing each other. if the foster or my dog dont try to crate fight, i do this for another week. if things go well, i have my husband take the foster to the fenced in yard on leash, and i take my one dog on leash onthe outside of the fence to walk but not meet. if that goes well then they can meet thru the fence. if that goes well after one more week then we take both dogs for a walk far apart. its a slow tedious project, and its better if the dogs are opposite sex. not saying a fight wont break out, though. keep all food toys, bones off the floor at alll times, only allow toys and bones in their crates w/the doors shut and locked. sometimes it works out and sometimes it doesnt. i always keep my fosterson leash the entire time they are here, this way i have a break in breaking up a fight if it happens. after that then i start all over again w/ the second dog here, then the third. i never let them all play together, ever. it takes about 2 weeks to a month for the foster dog to come out of its shell to feel comfortable in the house. you have to be very patient and diligent. and, very careful.