Cosmetic tip?

The only way to do them right is to tape off and spray. I touched up a spot on mine with a silver paint pen and it looks great. Try the paint pen again, scuff them up with some sandpaper, like 2000 grit and clean them off really well--take your time and put several coats on over a few hour period letting them dry fully each time. I think they will look fine...

 

As Robbie suggested, rough-up the surface using a fine grit sandpaper and make sure to use a sanding block.

This technique is easy to perform, but difficult to describe.

Get a good quality foam brush at Home Depot. Trim off the tapered end and cut it to the exact width of ALL the silver stripes on the cover - so as to form a "sponge on a stick". Get a disposable, shallow FLAT aluminum baking pan. Put in just enough paint to just cover to bottom of the pan with a very, very thin layer. Immerse the foam brush in the paint in a horizontal/flat orientation, let it absorb paint for about 3 seconds and then remove any excess paint by gently scraping the brush in a horizontal/flat orientation against the lip of the pan. Keeping the foam brush in a ABSOLUTELY horizontal/flat orientation, slowly and continuously moving it along the valve cover.

Alternately, you can purchase on of those painting sponge kits and trim it to the exact width.

You will have to repeat this several times to get perfect coverage, but it leaves a absolutely smooth surface, with no drips.

I used this technique to paint my 308s and 328 valve covers in situ. They came out as good as OEM.

 

I took mine off and using a sanding sponge sanded all the silver off down to the Alum . repainted the whole cover satin black and resanded back to the alum again and clear coated. so I have the shinny alum showing not silver paint, not as original but looks very nice.

 

Cosmetic tip?

When I told my girlfriend she drew her eyebrows on too high, she looked surprised!

 

you should be arrested for that one (can I use it?)