On Tony's bubbly black: Perhaps the undercoat has to cure for a few days. Today I bought a spraycan of "chrome silver enamel" and in the fine print it says "Avoid painting over fresh enamel, as the solvents may damage the coating." It doesn't explain "fresh".
I've no idea whether the solvents in mine are anything like those in Alclad but, looking through my "how to" notes from old SF posts, I see Nuvolare said he left Humbrol enamel gloss black for 48 hours before applying Alclad. (He said he'd read on the net that a gloss acrylic base could also be used.)
To my original question, driver#8 recommended PlastiKote (page 1), so I went to a hardware shop today and found this ColorPak can, possibly similar. The cap looks as realistically chrome as any manufactured slot-car trim parts.
Haven't tried it yet. Weather too cold and damp here for any proper test.