Lookin' good so far...
I have found that Eastwood's Aluma Blast is great for that fresh aluminum look.
They also make a "detail gray" that's great for looking like fresh cast iron.
I have tried most of the exhaust paints over the years on both cast iron and tube headers and found that the only thing that could be considered "permanent" is a ceramic coating.
The Eastwood stainless steel header paint did hold up well for several years on my Fentons, but eventually rust spots did start to appear.
Some POR-15 products require top coating, some do not. Just to clarify, "chassis black" is not the same thing as the product they sell for covering up rust. The stuff for covering up rust rquires a topcoat. It's best to wait to topcoat till the stuff can be touched, but you can leave a fingerprint in it. This way, no sanding is required.
I have used several clears over the years as well. The only time anything turned yellow was if it got ALOT of exposure to raw fuel. Some clears stain easier than others. Valve covers aren't exposed to gas, so don't worry about it.
I have used the Pelucid clear on my polished aluminum parts, and while it was difficult to use, once i got it right, it's been on my valve cover now for something like 10 years now without any issues. I have some of there two part clear, but I haven't tried it yet. Supposed to be easier to use than the Pelucid.
If you are going to clear a polished zinc or aluminum part, be sure to clean it with something like denatured alcohol, not mineral spirits or lacquer thinner. It needs to be absolutely clean. Baking-cleaning-baking-cleaning will help get all of the crap out of the pores of the metal. Especially necessary if you are going to be baking a coating on.
Metal prep type stuff will ruin a polished surface, so avoid using them. Ok if not polished.
