
This is what Lesley from the EASBTC (shes pretty famous in the dog world!) said to me a week ago when I asked her the same thing as we are introducing a new male pup to our female SBT and she is just over 2 years old.
I would probably make the introduction indoors (bit cold for a puppy to be outdoors for any length of time at the moment) but yes, letting Mitzy sniff at the pup's bottom is sensible then I would just pop the pup on the floor and watch carefully. Mitzy may well give the little lad a good sniffing and clean up and even push him around a little, and he may well hang on to her neck and give as good as he gets but so long as you don't let things get out of hand it is good for them to find their own way. Most bitches or even males will tolerate puppies nipping and will then put them in their place when they have had enough - which they should be allowed to do so long as they are not overly rough - from your description of Mitzy I doubt she will be. I don't think I would worry about separating them with a baby gate as the pup will probably just squeeze through it anyway! If the pup is being a pest with Mitsy then just take one of them out of the equation so she gets some peace. My advice is always to separate them when you aren't supervising - better to be safe than sorry. Even a dog and bitch that have grown up together can fall out over the silliest thing.Just got to ask, are you getting a female puppy to go with your boy?
As 2 males might cause big problems later on with bull breeds, a male and female are ideal as females usually rule the roost lol