Riso and Hudson's general instinct explanations are the best. I also like their levels of health for type, they seem quite accurate to me. In that way they can help increase self-awareness and self-monitoring.
Naranjo is better for core type motivation and exposing people at their worst, although he's too in love with Freud for my tastes. With him I think it's important to remember that most of what he says is metaphorical not literal, and I think a lot of people have a hard time grasping that. You have to think big picture with Naranjo, not specifics. Lots of extroverted intuition leaps in his thinking and associations.
When I read Naranjo I was torn between 4w5 and 5w4 for myself. He made the core four obvious once I read about fours being more 'wet' in their sorrow while fives sorrow is more 'dry'. (I'm paraphrasing, I can't remember what it was exactly.) Also what he said about sexual fours qualities being close to borderline personality disorder*. When I'm unhealthy the borderline traits kick in, for sure. When I'm healthier, though, it's harder to see. That's another thing about Naranjo, you really have to focus on how you are at your worst.
*Overall, the features of BPD include unusually intense sensitivity in relationships with others, difficulty regulating emotions, and impulsivity.