The Retail Method is putting junk in the retail flea market slots (ex: shells, flowers) and selling them for 999,999 bells, then dropping the bought item outside so it can be put back in the slot. So if you were to be giving me IGB, you would come to my town and go in my ReTail and buy the items, then go back to the ATM and get more bells to buy them again because it's just a cycle of putting the items back so you can put all of the bells into your account directly. I'm not the best at explaining but I hope that made sense, haha.