I'd probably use the paint-on masking fluid if I had to mask it, but it looks like a lot of the trim, lights etc are removable, so in theory just key the surface, and spray the whole thing, then repaint the black around the windows etc. I'm toying with the idea of repainting my 1:18 2CV (as it's a bit sombre in dark grey...for my tastes anyway) and this would be similar in construction I think.
But... I'd be happy enough to leave it red unless I was sure I could get a good result, so until I have one in my hands...
Ray The Fleet (most recent first):
2000 Citroën XM 3.0 24V V6 Exclusive Auto (pre-MOT)
1997 Citroën XM 2.0 TCT Exclusive Auto (for sale)
1979 Citroën CX 2.4 EI Cmatic Prestige (slowly being restored)
1992 Alfa Romeo 164 Lusso 3.0 v6 12v Manual (on the to-do list)