Silver solder - extra soft or extra easy. Lowest melting point. 5 dwt or about 7.8 grams. Cut into small pieces (pallions) to use. Don't get the various solders mixed up when they are laying on your bench. Colour one side with a felt pen or highlighter if you are inclined to accidentally mix things up! Or cut it into distinct shapes, i.e. triangles vs squares, etc.