If it’s a weekend night in August, Mike Martin will check mics, make sure all lights are working at the Brenau Downtown Center and get ice for the cast and crew of “Smoke on the Mountain” before checking in at the box office and getting into costume for show time. When the entire cast meets him backstage, a group prayer is said and the show begins. The only difference this August for Martin, managing artistic and technical director for the Georgia Mountain Players, is that after 21 years, he is doing this for the last time.