For a detailed guide on returning your Ripto Bux from Ethereum to Waves, consult this handy text document put together by USUKAN (a very helpful and very active member of Waves, Incent, and Ethereum communities.) --> https://mega.nz/#!GE4iFRTA!7aeiWq5VGFyoNcmyesQrGo-aWyrkrm_laWGTS5sMeJE
(Note: It costs Etherum gas to make transactions on the Ethereum network just as it costs Waves to send a Waves transaction fee. So, be sure to have or purchase a few Eth to insure you can swap your Ripto Bux back to Waves.)
(Note: Moving your Ripto Bux back to Waves will have no impact on this airdrop.)

Hope this help,just download the .txt file for more info.