Any of the options listed in those threads will work (radiator paint). One problem with paint, though, is that it chips from rocks and road debris very easily and will look like ass over time.

One other option is a Thermal Displacement Coating (TDC). This is a powder coat that actually improves heat transfer, and is much more durable than paint. I'm not positive if any of the local powdercoating shops actually do TDC coating, but it might be worth looking into if you want to do it right the first time.