Oh Boy, Mike, you already have the lowest flux residue solder made, if in a thin gauge such as no. 20 wire gauge! I would not and did not use anything on ANY of my kits including the K2 but Ersin Multicore Solder. The company is now known in USA as Multicore Solders, and is stocked by McMaster Carr among others. (Distributors). GL! Stuart K5KVH