Having a look on skyscanner, the quickest way seem to be flying Qantas to USA (SFO, LAX, DFW) then onwards to Toronto.
Have a play on the website using multicity tool for Qantas and searching the individual legs on Virgin AU. It is a populat route (across the Pacific) so which ever way has seats available is a good way.
I personally use a Citibank Debit Card to withdraw from atm once I land at the airport. I use credit card as much as possible and minimise cash usage and withdrawal. If you use a creditcard, I use a no forex card or one that earns more points for oversea spend.
Mobile wallet generally gets you from the poor exchange rate. My way above gives me a rate pretty close to forex rate from say XE.com.