Holly doesn't do at all well in the heat. Her last groomer shaved her belly and she seems a LOT cooler and happier. I was afraid that it would look funny but, I never notice it until she rolls over on her back. You can see that it is hardly noticeable. We will probably keep her like that in the interest of her comfort unless we are going to visit any areas with cold climstes.
When we were breeding ans showing Maltese, we used a cooling fan which attached to the mesh door of a Vari Kennel. The cooler included a plastic frozen insert which acted as a small battery operated air conditioner.
We are thinking about either of these two vests for Holly, both of which seem to be used for military dogs: