I've eaten at a lot of places who cook skewers like this, and surprisingly I have never noticed any ashy skewers. I haven't really noticed the technique, but I think they fan them first to get any loose ashes out and heat up the coals before putting the meat on. The other thing could just be the fanning method, they could fan it in a way that the ashes spread out to the sides rather than getting up into the food. But now I'm just speculating. I'm sure they would love to have an infrared grill, but I think it's a little out of their price range. The thing about these charcoal grills is that they're cheap to build and maintain, plus they do also give a nice smokey flavor that I'm not sure you could get from an infrared or propane grill setup.
