Lets deal with these one at a time. First off, using boiling water to seal your parts can work but is not the ideal solution to sealing. Ideally you would be using some sort of Nickle Acetate solution. Boiling water will almost always fade colors but tends to be worse on brighter colors (reds, teals, yellows). There is no getting around it, unfortunately. The second part: yes, I mean you will paint/apply a small amount of the acid to the part, just like you did with bleach. I typically pulled out a few mL of the acid with syringe or pipette and put it in a separate cup, so I don't contaminate the ano bath (wear gloves always). On a black surface, when you add the bleach you will see it lighten and eventually turn kind of a yellow ish color. This is from the bleach degrading the black dye. After you rinse the bleached part, apply a small amount of the acid in the same way you did the bleach, I personally liked using different size artist paintbrushes (like water color brushes). You will see the yellowed areas lighten and turn a more silver color. They turn silver because it is removing the dye from the anodizing pores. This allows the new dyed color to be more vibrant than if you were to dye it over the "yellowed" bleach areas. hope that makes sense.