Angel food cake pans should only be used for angel food cakes. Angel food cakes rise and get their light featherly texture from the beaten eggs, since they do not have any leavening. When baked the batter needs to cling to and climb up the sides of the pan.
If your pan has fat leftover from another type of cake, the batter will not adhere to the pan and you will not get proper volume for an angel food cake.
If you never plan on making an angel food cake in your pan- then you can use it for making a bundt cake. Follow the bundt cake recipe. You may need to bake the cake slightly less time- check it with a toothpick for doneness.
Thanks for your question.
Answered 11/06/2012 by jturnbull