The videos cover that. You more or less take them out with you into the world and feed kibble around strangers dogs and whatever else happens to bother them. If they have high prey drive you can play with them with a puppy shammy or tug etc.
The basic idea behind it is you aren't just exposing your dog to things that are potentially scary to them and allowing them to decide on their own if it was a positive experience. You are using primary or secondary reinforcers (toys and food or praise) to engineer good vibes around the potential triggers. Direct interaction with the strangers or dogs is unnecessary, and depending on who you ask or what your training goals are, potentially detrimental.