I'm going to copy and paste all training tips to my dad, so feel free to give them!
I got my dad a Mini Schnauzer after their shelter dog passed away (another Mini Schnauzer). Mr. T, their new dog, has been horrible, with his behavior and I tried back then to get them to NILIF. But dad said "Oh he just gets treats because he's cute" instead of making him "sit" for treats, you know what I mean.
He has been aggressive with people, when they lived here in this area, they'd crate him when people came over.
Well since they've been gone for the past few years, apparently he's gotten worse and as a woman was walking by the other day, Mr. T ran out and bit her. I guess he was in the front/unfenced yard (I have no idea the setup, they live in Alabama now) and this gal was walking by but dad had gone back in to get a coat so wasn't out there with the dog. He is now keeping the dog on a leash but Dad's pretty upset, of course. And he's not sure the dog bit the woman, she said he did but she's also, it sounds like, a bit unbalanced anyway. If it happened it sounds like it did not break skin.
Anyway - he was commenting this AM about getting an electric collar for the dog. I sent him a link to NILIF. They've never done this with the dog.
My theory is that they must respect you before they'll listen to you at all, I've learned this after fostering and working with hundreds of dogs, through my own observation. Once you establish yourself as leader you can train easier that is.
Anyway - anyone else got suggestions other than avoidance of the situation and NILIF? Apparently there's no plans to fence the home (they live with my sister and her husband).