The advice you received is correct but lets summarize it.
1.You say you are in the U.S, and Australia so those countries are covered.
2.Any other countries should pay either through PayPal or have them pay directly to your account -in any case it is your customers responsibility to pay you.
3.If you have customers that don't have the possibility of money transfer to your account then you have to accept credit card payment from them.
4.If they don't have a bank account at all then they it is a cash transfer to you.
5.You pay to your suppliers by credit card- check which gives the best service the U.S. or Australian Bank
6.Remember better have all the money at hand and pay a bit more for bank transfers than trying to save 1%-2% but not gaining control of the 98% of the money