Hi Catherine, welcome to Rabbit Talk!
I live in NW Oklahoma where we get weeks of temps above 100F!! And I raise English Angoras too!
What I have found to be most effective in keeping my buns cool in the heat:
1. Positioning the hutch under a shade tree makes a big difference, but I also recommend a wire cage rather than a wooden hutch.
2. Watering under the hutch/cage and around the tree in the morning helps lower the temperature and also helps the tree with convection cooling.
3. If at all possible, a ground pen that gets shade the majority of the day will help most of all. It allows the bun to move around to seek out cooler earth (even if they have to dig for it).
As for angora fur, it insulates "both ways" ... keeps the cold out in the winter and can keep the heat somewhat moderated in the heat.
You can also shear the bun, or at least take off some of the belly fur. Yes, most of the heat is dissipated through the ears, but they also can gain cooling through the belly.
When my buns are in the runout pen, they dig under some planks I fastened together lengthwise and laid upside down. I also made a square from leftover tin that is laid over the planks with a large tree stump to support the free end. The buns love to tunnel under that, but they can also be seen dancing around on top when it rains!!
Good luck!