Bumblefoot in chickens is usually caused from jumping off roosts or can be a result of rough wood on roosts(i sand down all my roosts). Unfortunately sometimes surgery has to be performed on bumblefoot. Definitely try other methods first,but if they do not work then surgery has to be done,otherwise staph infection will spread. Removing the pus can be a challenge due to the fact that it forms a hard core,in other animals it is fluid like.