I teach stained glass classes for the local colleges and the one thing that I've found most helpful is this: the more you act like you know what you're doing, the more they will think you know what you're doing. Oh and also try to look the part. Then you just dazzle them with a few techniques, show a few secret tips and tricks, show some finished works, and then let them think their way through things on their own and answer questions. With only 1 hour you won't be able to go into too much detail so just paint with broad strokes on some topics you know like the back of your hand. The more you go outside of your comfort zone the more you look like a novice so do what you know and it will flow so naturally that you'll automatically come off like an expert.