First part (clutch cover) was painted, and I have to say it was a complete success!!!

I followed your instructions about the cleaning with some more additions. First I left the parts sucking in oxalic acid solution overnight. The etching procedure gave me this:

After I've sanded everything, really, really, really (and I mean it) good, I sprinkled everything with water and cleaned them dry with a lint free cloth. Because I was too excited I forgot to take a picture of that stage...

Then the painting. I used spray paint (matt black) suitable for up to 800 Celcius (do the math for Fahrenheit...

)

I've read somewhere that these paints cure better if you "cook" them with a butane torch. Why not? I gave it a try and it does work! The paint cured and it got really tough.

I've also painted the alternator cover the same color and the oil filter cover, sparkling silver. On silver parts I'll paint a clear glossy varnish.
My next step is the crankcase. This is the most difficult but I will come out as a winner!!!