The process I followed was:

* create an account on binance.com

* transfer the stellars there, making sure to follow the instructions about the MEMO_TEXT.

* convert the lumens into bitcoin

* transfer the bitcoin to coinbase

* sell it.

There is probably a more optimized or less expensive way to accomplish this, but this was the easiest way for me, and binance did not require a social security number or photo id like some sites wanted.