Curious, why would you do that? Why wouldn't you transfer coins to a wallet you control and then conduct the transaction from there? Doing it from Coinbase throws away anonymity -- why not just buy your drugs with a Visa card then?

that's the recommended course of action, IIRC.

personally, I prefer to do all my gray market drug purchases on the ol' regular internet with a prepaid debit card.

How do you get the prepaid card?

Cameras are so cheap that practically every shop has them. Voice, face, body recognition are getting better by the week and can be run on all recordings.