Or 2 bankers drafts, one for the settlement one for the balance. Simply take a walk around to the post box with a draft and the settlement letter in an envelope and send it to the finance company
On a side note Don't assume that a bankers draft is a safe way of taking money for a car, after all how many drafts do you see, how could you spot a real one ?, the only way I would take one is if I went to the bank with the buyer and physically see it done, other than this then you need to waitnfor it to be cleared funds in your bank account