I'm a rubbing! Rub Rub Rub! 

Haven't rubbed this much since i was a teenager! lol

Any cleaner that might help? 

Hand polishing those things will be a chore! A buffing wheel on a grinder would make quick work of them, but of course not everyone has a bench grinder that could be used for polishing, so...

I would suggest a metal polish such as Flitz, or Mother's Aluminum polish. Either will require a lot of elbow grease, and will turn your fingers black. A quick rub-down with some Scotchbrite pads before buffing will also help clean, and smooth the surface for buffing. 

Here's some of my last polishing job...'81 Goldwing 1100 engine stuff. Set up one of my grinders on my rear deck railing, and mounted a buffing wheel to one side. I bought some buffing compounds to use for this since it would work better for my set-up. Did pretty much all of the exposed aluminum stuff, and it all took me several weekend days to get it done. Even using a buffing wheel, my hands got nasty! I would highly recommend using latex/rubber gloves! 😁

Well, this is ther best I could do!

I'd say overall they came out nice. For the spaces in between the fins, you could paint that area, and make them stand out even more. It's really hard to get down in the to polish, so putting some color in there makes the polishing effort on the areas you can get to worth it.

I have to agree with Mr. Apple, those look darn good!  Had those valve covers on "The Toy" and always liked the look of them.  Putting a dressing coat of some sort on the exhaust manifolds will add to the appearance.  Nice job!

Thank you..This is all new to me..What type of dressing coat do you recommend for the exhaust manifold?

I used Calyx Exhaust Manifold Dressing on my factory manifolds. I thought it worked really good. Kinda messy but so far it has lasted several months. Sorry, not sure where I picked it up.