I haven't used Metal Rescue, but i have used Evaporust which looks like essentially the same thing and it works well. It's great for getting rust off old bolts and smaller items. I soaked an old chrome bicycle wheel as a test and it didn't do anything but take the rust off. Sorry, no pics. Waaaaay better than grinding and sanding!
I picked it up from a distributor in Dallas so I didn't have to pay for shipping. It was about 7 years ago, so I don't remember who the distributor was.
http://www.evaporust.com/index.html