The problem is that there is no way someone can guarantee you a 100% success rate. There are so many things that can go wrong:
Coinbase not verifying your account for months.
Coinbase not receiving your bank deposit and taking 3 months to respond to your ticket.
Poloniex refusing your withdrawal and never answering to your requests.
I hear every day of hundreds of people that did everything right, but still didn't make it. Just be careful, this is still the wild west.
I would recommend you never take the Lumens from the exchange. Most exchanges like Kraken are much better than you at dealing with security. It's also easier to sell them if you have them directly on the exchange.