The trick - seriously - is to visit a poor doctor in a poor area of town. Get your textbook list of requirements, pay cash for your appointment, and be the perfect patient. Each time, ask for a little bit more painkillers for a little bit more pain. The doctors want to cover their asses legally and not go to jail or get sued, but it's no hair off their back if you're a lifetiem "pain mgmt" candidate living on Roxy for the rest of your days.
Be polite, be cool, know what you want, be patient, and do it at a doc in the crappy area of town, even if you hate sitting in line at the clinic. Just give the same story... find the symptoms for a degenerative back condition which doesn't show up on xrays, maybs soft trauma, and run with it.
I have used vicodin maybe 3 times in my life, and avoid painkillers altogether. but my bro ran a pharmacy, and he always saw the people piping in from the same certain doctors for years, with progressively bigger painkiller loads.