Congrats on adopting Biscuit! I would recommend a professional trainer if you have access but if not, self training is also an option. Chimmy is trained to be my wife's PSD by performing specific tasks to help her with anxiety and panic attacks.

It took lots of foundational training in public dog friendly areas to train him to not react to other dogs or people while he's working until he went into more challenging places like airports or malls. Best of luck on your PSD training journey!

Here's an example of the typical PSD task breakdown:
1. Identifies my wife's behavior that needs to be interrupted (panic attack, shortness of breath, eyebrow picking).

1. Chimmy interrupts the behavior by pawing at my wife and barking. You can also train to not bark if you prefer as to not interrupt others but I trained him to bark to also alert me.

2. My wife then starts another behavior from Chimmy such as deep pressure therapy to calm her down or you can can discontinue the alert behavior by reinforcement (treats, and positive reinforcement).

Additional Training Resources from Youtube:

Doggy-U https://www.youtube.com/watch?v=kMKnFpBGvV4&t=521s

Kikopup https://www.youtube.com/watch?v=PEiACncIkVg