For many years American PJ1 was the default paint of choice for anything black and many things silver. Shipping restrictions and the inevitable Health and Safety saw it absent from shelves for several years but it’s recently returned, reformulated, but still viable especially where high temperature applications are involved. The Sperex brand, once well known, seems to now be sold under the VHT banner but there’s a raft of alternatives on offer nowadays. The likes of Tool Station and Screwfix offer their own versions as do companies such as RS Components and Wurth, not forgetting the Halfords, B&QS etc. of this world. Almost without exception high temperature paints are applied directly to bare the metal but more decorative finishes are generally applied over an etch primer which chemically bonds itself to alloys, providing a strong key. Ultimately there are loads of choices so do your research before buying.