I'm no trainer, but if he were mine, I'd give him some one one one and take him out by himself. At the same time, I'd set him up for success by provided some high value treats and ask ( strangers to him) others to give home treats and, when willing some positive attention.
Nothing is as simple as it seems or as complicated as we make it~
Attitude is everything -- Pick a good one!
Sofie AKA Ussina vom Haus Brezel
Jack von Jagenstadt
Tatty - Burmese bad cat