I did my pulley in grey phosphate, came out great, also did the fan pulley, as the back was definitely grey phosphate in color. I used the Palmetto chemicals, get the grey phosphate and black manganese which is used on most of the bolts. Get a small electric burner, do not do indoors. I have a double one from Walmart and get a small and large porcelain coated crab pot, also from Walmart and cheaper than stainless steel. I use the small pot for bolts as you don't need to heat up a ton of solution. Also if you strain the used chemical with a coffee filter you can reuse the solution with great results over and over again.
Also parts must be cleaned either by sand blasting or with bolts I use a wire wheel.
Results are great, but I never thought about using distilled water from the thread, so I am going to try that, as once in a while there is some streaking.
I prefer to reuse an original bolt as opposed to the reproduction stuff if I can help it
Mike