the method archiben described is the same method I always use, But I typically use a very bright blue colour, so that if it reflects back, it won't necessarily look bad, I guess I've always assumed if it is visible it might look like a sky reflection, or something of that nature. As far as the anti-aliasing goes, a steady hand and a brush tool are all I can suggest for that.. oh and 3200% zoom
HTH,
dan