restoring pot metal

There is a guy who comes to the local flea market and demonstates repairing broken pot metal, cast aluminum etc.. He sells the special welding rods ( 1 foot stick for 1 dollar ). They are said to be a blend of aluminum, zinc, etc.. I talked with another guy who once worked for this seller at another flea market. He said the secret to success is very very low heat and keep the rods stored in a air tight container to keep them bone dry. To let them absorb any moisture and even using on a rainy day will effect their performance. Oddly enough they are sold unwrapped. 3 pieces bound with a small piece of tape for 3 dollars.
Also , I was very impressed with the spray chrome product shown ( video ) at Leno's Garage. Fool proof application and eco friendly too.
I was disappointed by that chromesolutions.de website.
I hope they get affordable international sales available soon.