Nasals are dangerous because our subconscious tells us that they must be very voiced. In many cases this leads to an attempt to push them to the nasal cavity by force using a completely cramped tongue. This is especially true when there is an insufficient resonance form).
In this case it helps greatly to realise that if we work in the correct singing manner these consonants will sound on their own, and that there is no need to help them in any way.