I’ve run lots of participation games at shows as part of a club, and individually at more focused wargaming events. Ive done the odd demo game too.
It takes lots of design work, a certain amount of prep and it is useful to have team support on the day. We have a fairly tried and tested formula for show games in terms of approach (but a very varied range of subjects).
"Mistakes in the initial deployment cannot be rectified" - Helmuth von Moltke