At Columbus there was a guy who was a sim operator and local FBO operator who did the test prep, administration, and FSDO stuff. He got us the info as we got closer to T-1 graduation. I don't think it was expensive. Did a half-day study session with the guy, took the test in like 10 minutes, and I got the commercial pilot, multi-eng commercial, and instrument ratings added to my private privileges.
Still don't really know what all that means...