The MSC created the Bill.com account for me, but to get the money transferred to my bank I had to log in to Bill.com and provide my banking information (Got to Bill.com, click the "gear" icon in the upper right corner and choose Settings. You'll see a link labeled "Bank Accounts" and you can provide your bank info.) Once you've done that, Bill.com will automatically transfer the money to your bank every time a payment arrives. Bill.com transfers the money within 24 hours and then your bank has to process the transfer.
Sentry uses this Rube Goldberg payment method. They already won the battle for slowest-paying MSC, but this secures their spot.