I would think that the best approach would be a clean test case, within the 5th Circuit boundaries, for violating some existing federal law (maybe Brady or some portion of the 1968 Gun Act). Presumably either a lower court or the 5th Circuit Court would then use the Emerson holding to invalidate that (portion of the) law as a violation of the 2nd Amendment. At that point the federal government could either appeal to the U.S. Supreme Court, or else someone in another District who was convicted of that law could appeal to the USSC. The USSC would almost be forced to take up the issue to resolve the conflict.
Assuming the USSC substantially adopted the Emerson holding regarding the 2nd Amendment being an individual right, numerous federal firearms laws would immediately be invalidated or be sharply limited. At that point a new test case against some state gun-control law could be appealed to the federal courts (preferably within the 5th District), as a lead-in to Incorporation. And if the USSC ultimately incorporated the 2nd Amendment via the 14th Amendment, a huge array of state gun-control laws would come tumbling down.