You must make sure that the specified brush is no longer used by any widgets in your GUI before you call this function. Note that under normal conditions it is not necessary to call this function because normally all brushes are freed automatically by MUI Royale. Under certain conditions, however, it can be useful to call this function.
MUI Royale caches all Hollywood brushes that you use as images in your GUI. That is why when you try to use a Hollywood brush in your GUI a second time, it will just be loaded from MUI Royale's internal image cache for performance reasons, regardless of the brush's current contents inside Hollywood. This can lead to unwanted behaviour in case you have updated your brush's graphics in the meantime and you want MUI Royale to use the updated graphics. In that case, you first have to free the brush in MUI Royale's internal image cache by using this function. When you pass the brush to MUI Royale again then, it will be re-created from the brush's current state and it will be cached anew.