how is the conjugation мазанет derived? My dictionary says мажу, мажешь...
мазать -> мажу, мажешь

промазать -> промажу, промажешь

мазануть (very informal and colloquial) = промазать

Formally speaking, there's no such word "мазануть". But if it existed, I'd say:

мазануть -> промазану, промазанешь

But that sounds foolish. Don't say so. There are no such forms.