It's worth pointing out that the original Dunning-Kruger paper didn't find that the ignorant are more confident than the knowledgeable, only that the ignorant are overconfident and the knowledgeable are underconfident.
Many people have in mind a curve of confidence vs knowledge[0] that looks nothing like the curve from the paper[1].
It is apparently not confirmed in other cultures, where interpersonal relationships are traditionally conceived of differently.
Corresponding advice from http://highexistence.com/dunning-kruger-effect/: Be confident in the areas that you suck at.