I might suggest using a Brass tumbler for firearms with crushed walnut media that has the polishing compount on the walnut. It will remove old paint but leave the plating if it is still intact, while polishing the metal to a nice new shine. If you are to attempt to blast the metal with anything other than soda or plastic media it will change the surface structure of the metal and the Cad/Zinc plating will not even look close to what it looked like originally.
THe Brass tumbler that I am talking about can be had at "Midway" with the media for 50-75 dollars.. Works great.
http://www.midwayusa.com/viewproduct/?productnumber=514805
J