Down south I just run a gel ice-pack on back of my neck on long street rides. Fools my brain somehow and I get goosebumps. I keep a couple of spares in a thermos and refreeze them at night.
Wearing a light and breezy helmet helps too. Love Airoh helmets! Even prefer MX helmets down here as long as the speeds are under 160 kph.
In Mexico you need a Hayabusa on the coutas and a MX or Trials bike everywhere else! That's why I avoid the coutas and some of the fast libres, especially Hwy 30 between Torreon and Monclova. Ran the cruise at 200 kph and still kept getting passed.
None of my bikes go fast so now I take the burrow trails instead.