Unfortunately I haven't yet solved the problem of how to (safely) send coins to coinbase, although I do have some ideas (but they'll leave traces that the coins were mixed)
That one is easy. send coins to bitstamp/bitfinex/btc-/huobi/ect. and then process the withdrawal. Using change addresses properly after withdrawing from another exchange will help with this as even if it is determined that the withdrawal from the exchange was from a casino, it would be difficult to know for sure that the coins were from the exchange.
