Musar --the learning of the books of the rishonim [mediaeval authors] that deal with ethical issues is helpful in terms of orientation. It gives an idea of the big picture of Torah. But the idea that learning lots of Musar in order to correct character traits, seems a bit far fetched. That is why I think almost all Litvak yeshivas based in the Gra limited the amount of time of learning Musar to only 20 minutes before mincha and 15 min. before maariv. But I am not sure if there really is any  formulas that can help one come to good character. So learning Musar certainly seems like the best approach in that there simply does not seem to be any other approach at all.

 I can see that without Musar people tend to understand Torah in ways that are idolatry in the guise of Torah. 

So for those with resources, the best idea is that original idea of Rav Israel Salanter to spend a lot of one's spare time in learning Musar.

Rav Nahman also noticed the issue that people can get the wrong idea easily about what really constitutes a "mitzvah". The is the very first Torah lesson in his LeM that היצר הרע מתלבש במצוות the evil inclinations disguises itself in mitzvot -