Having undercoated the Loco in Tamiya grey spary paint, I added the missing rivets to the smokebox. These were done using Archer rivet transfers - basically blobs of plastic on a carrier film. I went for a vague representation rather than trying to represent every single rivet. This isn't the best photo, but if you click to view it full size, then the rivets should be visible.

I'm now in the process of painting the loco, using Vallejo acrylic paints. The main colour is a very dark grey, rather than black, as the loco is going to be weathered quite heavily.