Bike fitting is something that only serious cyclist will bother with. Most people are usually happy with trying out a bike to ensure it fits well. Bike fitting is like getting a suit tailor made rather than off the peg. If you were spending money for a tailored suit would you trust a young good looking person or someone old who looks like they've been a tailor all their lives? Basically use a bike mechanic in the video, you don't want someone pretending to know what they're talking about. If you must use someone good looking have them go in for a fitting and video what goes on and have the expert go through explaining the whole process to them. Use graphics only where it helps explain points.