Blue painters tape is kind of a waste of money. I do construction and also paint commercial buildings for a living. Regular, cheap masking tape will have better adhesion. It should not leave a residue or be hard to remove if you take it off within a few days of masking. Masking and then trimming with a razor blade is a good idea, as posted by someone before me.
Steam cleaning works well for brackets and other items that are pretty greasy. My uncle has a trans shop and uses a dishwasher like machine to clean tranny cases and parts. They come out awesome. You could have a shop run some of your parts or try using a presure washer and degreaser (although the comercial steam presure washer from my work doesn't work nearly as well as my uncles enclosed washer). Lacquer thinner seems to work well for cleaning parts also. Scotch bright pads, wire brushes, and nylon brushes are some of the things I use for cleaning parts.
I am not a big fan of valve covers painted to match the block. It looks a little too boring. The black would look nice. I like the silver on the exhaust and turbo. My 385 has an orange block, oil pan, and timing cover. The heads, intake, water pump, valve covers, and distributor are aluminum, so they are not painted. My factory air cleaner, ps pump, ac pump, and brackets are black. I have seen iron heads painted silver or aluminum color and I think it looks nice also.
My freeze plugs are painted and it doesn't seem tacky. They just blend in.
Are you going to paint your engine bay also? I did mine when my engine was out. I used a gloss black industrial paint. It looked nice for quite a while but now it is getting beat up. I wish I would have use some automotive urethane paint. The guy that built my engine said a lot of people throw a nice clean engine into a beat up truck and it looks bad, in his opinion. My truck looked similar to factory when I was done. I got a lot of good comments on it. Mine is a nice resto/mod daily driver, definitely not a show truck, so I made the engine bay look good but did not spend a ton of time or money on it. The engine, however, got some nice parts.