A friend of mine recently bought a CD made by David Alan Stern - a guy who works as a full-time accent trainer. The goal of the CD is to teach you how to speak English in various accents, such as Scottish, Boston, German, etc, presumably to make you a more versatile actor. Problem is, the guy who teaches it doesn't sound very convincing. In fact, his attempt at a Scottish accent is almost unparalleled in its awfulness - has this chap even met a Scottish person before, or seen one on TV? By the sound of it, I think not.
Make up your own mind: here's a 15-second clip from the beginning of the CD. It's here as fair use (used for critique; a very short clip; doesn't remove value from the original work). Do you think that's someone qualified to teach other people how to speak in a Scottish accent?