One of the reason I didnt temp to change Halogen fogs to HID or LEDs. Last winter I was in Lahore and fog was really dense, it got worse if when turned on all 4 HIDs of the car, low and straight beam worked bit better.
on the installation, most cars have option to install front fogs. European spec car will have rear fogs as its required by law, the Asian spec cars rear fog lights have blanked out bulb place and can be installed with little effort. If no space available, buy an after market RED fog lights install by the bumber, more decent will be a cut out in the rear bumper though.