A thought about using ain't in conversational English

Ain't is the stigmatized, all-purpose negative particle of the underclass...and wealthy rock and country musicians.

No it ain't.

Re (Dude Who Knows)
"I ain't (don't) do that."
"She ain't (doesn't) kill animals."
I've never heard someone use the word "ain't" like this. That is, as a substitute for the verb "do".

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Some black Americans do:

I ain' do that = I didn't do that
I on' do that = I don't do that
I ain' doin' that = I'm not doing that

What sound does a bever make?

>>I on' do that = I don't do that<<

This is not exclusively an AAVE thing at all. It is definitely present in the speech of speakers of the dialect here (aside from AAVE), and this is particularly common in North American English as a whole amongst younger individuals in the case of "I don't know".

Even though "ain't" is usually avoided in educated or formal speech, I've seen speakers and even writers of formal English use it for emphasis. For example:

Do you really think the President will sign the bill? Ain't going to happen.

I think "ain't" would do nicely in the situations where Irish and Scottish speakers use "amn't": "I'm invited ain't I?". This avoids the use of 'are' with 'I'. I don't think it's very likely though.

I never use "ain't", not for emphasis, or for any purpose.