Thanks for sharing this!! think i'll be filling up my external drive quickly now! how does it work.. i.e. do I just comment on someones post and then they get it touch? I've never used google community before.
On the Google + community, you send them a Hang Out request to do the transaction. Normally you pay via Paypal or Google wallet, but mostly PayPal. It depends on what the seller prefers. You agree on a price, and send that amount. They acknowledge that they received it and give you the code. At first I would stick to the bigger sellers till you see how everything works. You can pick them out by, their frequent posts and 50+ codes available at once.