I finished AU's masters program just before my Maj board and have been told by AU once the results are out there will be two ACSC-correspondence "pipelines" to register for: the full one, and the "supplemental" one - basically a "top off" for the guys who did the Leadership or WIC concentrations of the Master's as a Capt. Take the 4 tests for the blocks that weren't covered in your Master's (the four classes that make up the "Joint Warfare" concentration, i.e. the "full" ACSC Master's) and you're ACSC complete.
Since you've already finished the Master's you DO NOT have to take the actual classes to finish - just the normal ACSC-correspondence tests for the 4 blocks you're missing.
On a related note - for those that haven't started a Master's yet, AU is hands down the way to go. Don't have to deal with TA (therefore no ADSC), 95% of the reading material is provided via PDF (maybe a book or two to buy off Amazon - not actual textbooks), the stuff you're studying is actually relevant to your career (military history, organizational leadership, doctrine, etc), and grading standards are not very stringent. I'll be honest, I pretty much min-ran it to check the box and it did not require much effort. However, I still took some good knowledge away from it, and it's stuff I can apply now versus after I get out. And I'm almost half complete with ACSC to boot - not a bad deal.