I wrote an article for N Scale Railroading about matching the Kato stainless steel color. See 047 May/Jun 2008 57 Stainless Steel Made Easy.
Initially, I was tinting Tamiya Smoke, but Mike Danneman simplified the procedure by just using multiple light coats of Tamiya Smoke. This works even better, just keep a sample car nearby to compare to as the coats are applied. The base silver in not important as long as it has minimal silver flakes. Currently, I am using silver from Vallejo and am very pleased with the results.
Marlin Cox