Short Answers

BCH can be mined.

Is there publicly available BCH miners right now?

• Not that I'm aware of

Can my old Antminer XX work on BCH network?

• I think this is a possibility if someone starts hacking it or bitmain comes out and releases updates to older miner software. They may even be able to do it right now with a pool.

Can I mine BCH with my GPU?

• Yes if there is mining software out there you can find that will work but will it be profitable? Not until difficulty tanks on BCH network back to "GPU mining" days of difficulty on BTC (not likely to happen since SHA256 asics exist, SOMEONE will adapt one of the many that exist)

Will it be profitable to mine BCH?

• This question is subjective to difficulty, price of electricity, and hashrate you can create. You will need to answer this for yourself by doing some math.

In essence the answer to "How to mine BCH" is that right now we are in a phase of "hurry up and wait" on the answers. Rest assured, once someone adapts an existing Asic to mine this network, its going to likely blow up to BTC difficulty levels from a few years ago and probably be worth less than BTC was during the same time since BCH is an "ALT" coin