I cheesed through a couple of classes in another way. There is a page that specifies the priority of classes. I then used that table to get 10 levels of a class that I liked running, warlock, and then 10 levels of the class that I basically wanted to skip. Since the counts are 10 vs 10, the priority table indicates which class will be credited at TR. You can still take all the enhancements from your favored class, and spend some/most of the skill points on that favor class. But you may miss out on the feats. I did not use that life for an ETR since the character was somewhat gimped.
You cannot do with trick with all combos. Some classes have alignment restrictions that prevent multiclassing this way.