Regarding the sheep pooh, I think that you are thinking of a "dagg" which is literally what you said, encrusted sheep pooh hanging onto a sheep's fleece. The New Zealand comedian, John Clarke, became famous in NZ as a character named "Fred Dagg". He had a hit in NZ with a version of Billy Connolly's "If it Weren't for Your Wellies", but being NZ, it was "If it Weren't for Your Gumboots". So yes, a dagg is a pretty low class, scruffy individual, probably with bad hygiene! 😁
A drongo is a bird native to North Australia; the slang term had pretty well the same meaning as "nong". 😁 I doubt that the bird was particularly stupid; the term probably came about just because it sounds kind of dumb. 😸
I believe there is some of Fred Dagg's stuff preserved on YouTube. He was a pretty funny character. John Clarke eventually moved to Australia, like a lot of NZ entertainers, because the NZ market tends to be a bit small.