I am working on a fat client legacy C++ application which has a lot of business logic mixed in with the presentation side of things. I want to clean things out and refactor the code out completely, so there is a clear seperation of concerns. I am looking at MVC or some other suitable design pattern in order to achieve this.

I would like to get recommendations from people who have walked this road before -

Do I use MVP or MVC (or another pattern)?

What is/are the best practices for undertaking something like this (i.e. useful steps/checks) ?