OK I'm the queen of positive training but we had to resort to a squirt gun. My husband works from home and Loki cannot just have barking fits whenever a dog/person walks by. It's OK if it's the doorbell or mailman or UPS, but he would bark at every single person that walked by. We got 2 mini super soakers and used them for about a week and it stopped. Now he just huffs and puffs at the door but doesn't bark if I ask him not to, unless someone actually comes UP to the door. They can now quietly watch people walking by. Sam barks some but only once or twice and Loki tends to set her off most of the time. She quiets down quickly while Loki struggled with that - he could bark like crazy for like 2 minutes.
You have to combine this with positive training of course - rewarding them for being quiet or quieting down, teaching them the commands... we just had to use this to interrupt him because he just couldn't quit barking once he started and I didn't want to pick him up.
Another way is to leave the leash on and remove them from the situation (in our case the patio door) and reward them for quieting down.
Now I just have to say their names and get their attention and say no barking and hold up my hand... they just had to learn the rules. Now that they know them it's easier to enforce them
Good luck!
ETA: As far as outside, have approaching people give her a treat or distract her with a treat. We had to work on that for a LONG time (like years) with Loki and he lets strangers pet him now. But we had to work on it a lot...