Look in your Coles/Woolworths catalogue each week, once every few months (typically around gift giving occasions like Xmas), you will see a promotion "Buy a $100 Coles Mastercard gift card, get 2000 points" as we know, 2,000 shopping points equals 1,000 frequent flyer points. So use your high earning credit card (1.25pts/dollar) to buy the $100 credit card and you will get 1000 FF points for the promotion and 125 pts from the credit card spend, ie. 1125 points for the $100 card, which is 11.25 points per dollar.
NOTE: the above is a simplistic view to show total earned is 11.25 pts per dollar and does NOT take into account the card purchase fee which is normally about $5.95 and is missing the ATO debit card fee of 20 cents per debit card transaction...... if you add this into the maths and base your FF points as worth 1 cent each, you will come in with a true earn rate (aka profit) of around 5 pts per dollar