You've got a cast iron pot and it's rusty. This is not an uncommon problem and it can be dealt with.

Before we get to cleaning let me tell you that once a cast iron pot has gotten to the point where it starts rusting the pot is no longer seasoned. So basically you're starting with raw cast iron. Given that, whatever you do to it won't hurt it at this point. However, don't use rust inhibitor or any acid to clean it. Clean it by mechanical means only!!!!

How rusty is it? 

Do you think a steel wool pad will clean it up? If, so get after it. You can use a Brillo Pad, regular steel wool; it doesn't mater. Scrub the heck out of it until all the rust is gone. 

If the rust is really bad, I mean thick, it's just going to take more elbow grease. You can use a scraper, heavy sand paper, even a drill  with a wire cup brush as shown to the right. "Wear your safety equipment when doing this."

I would stay away from high speed buffers; it's too easy to hurt yourself using a high speed buffer in a closed in area such as a pot.

I wouldn't have it bead blasted although I've heard of it being done. The beads don't necessarily scare me it just what was blasted before in the machine. You could wind up impregnated the cast iron with a toxic paint. I just wouldn't go there.

Now once your pot is cleaned up nice you can stick it in the dishwasher and wash the heck out of it. Put it on "heavy load" or "pots and pans" or something like that. Let it go through the heated dry cycle.

Once it's done you can begin to season it. Read about seasoning here. Cast Iron Seasoning.