Adding separate flight same day for baggage
 

Used miles through AA to go LAX-Brisbane (on Qantas). Booked separate flight, same day, to go Brisbane to Gladstone. Called Qantas and asked about adding flight due so I don't have to go out security, grab back, then go back through. They said I had to go out. Anyone have luck adding a flight (I get free luggage so that's not a concern, it's leaving secure area and rechecking)?

Similar to arriving in the US, you always have to clear customs and immigration (and security for that matter) on your first port of arrival in Australia. So QF is right, there is no way how you can arrive on an international flight and not having to re-check you bag.
Having said this, your bag can still be tagged through, meaning the tag will show Gladstone as the final destination and after passing customs you can just re-check it at the transfer counter. You also have to go through security again after changing terminals.

In BNE, the International Terminal is about 2 km from the Domestic Terminal. Its a bus or train connection (or walk - which is perfectly pleasant (sometimes)). As per the above, there is no option but to leave the International Terminal landside then go through security again at Domestic. Fortunately, security in Oz is relatively painless and lines move quickly (think 5 min max). No domestic ID checks, shoes stay on (unless full of steel). If eligible for entry, the QF domestic lounge is better than anything you'll find in the USA (almost anywhere).

http://www.bne.com.au/to-from-brisba...t-transfer-bus

You arrive in Brisbane and head through customs/immigration and collect your bag.

As soon as you walk out the glass door head right towards the rental car desks and in the far corner are a couple of Qantas check-in counters and Virgin ones as well.

Check-in here and they will take your bag, give you your boarding pass and a train or bus pass which you can use to get the domestic terminal. The train/bus pass is free so make sure to ask for one otherwise be prepared to pay around $4 to travel between the terminals.

Also if this is your first time travelling domestic in Australia you will be pleasantly surprised with the experience of going through security. It will be VERY different from that in the US.

I used the bus in August 2015 going INT->DOM, and I don't remember a bus pass. I thought we just waved our QF boarding pass. Is it new or have I forgotten it?

Yeh I've been given bus/train more recently but that being said I've also got away with a flash of the boarding pass.

The bus is now free anyway so I don't think the bus pass really matters unless you want to catch the train.