I am helping a friend that is exactly in the situation you mention. He is a HW guy that used to work with C in the past.
I think the best approach is mentoring and coding. I explain him a few concepts and then ask him to program some code. We just built a simple calculator in multiple platforms (WCF, Silverlight, XNA,..) and using some well known patterns (state, MVP...).
I force him to use good programming practices and refactor the code by asking him new features based on his mistakes. For example if he coupled a couple components like the View and the Controller I would ask him for a new view... this obviously makes him to rewrite a bunch of code and he realizes there are better ways...
In this way he is the one coming up with the natural decoupling and what is more important the "why is good". I am very pleased with the results so far; he is very happy with unit testing and how it allows him to easily change the code for good.
IMHO separation of concerns and unit testing are better explained and understood by coding and having to implement new features; specially for new programmers. Once he buys in I would recommend him to read "Design Patterns" by the GOF or some of its simpler varians.
