I did one. Your start time is the time of your receipt for gas. Doesn't need to be signed by a cop. Just some witnesses that you were there and they should verify the odometer reading on you bike. This should be done just before you leave. It cannot be a fellow participant in the ride or a family member. We grabbed some clerks at the truck stop we started from. If I recall you need 2 or 3 people.
Keep receipts for all gas (they must be time/date stamped) and keep a log of where you stopped, how long, times, etc. Time stops at the end, you must get a time dated receipt at the end, (just get some gas). Get someone at the end to confirm you were there. Send receipts, log,
map of route and registration form to them, along with your cash. You get a license plate backing (cool), sticker (its on my windshield) and ride pin.
See the website that javawave pointed out. Its not easy and I suggest you go with another biker to keep each other motivated. They have a bunch of other rides if you're insane (sorry, I mean so inclined).