Sunny is a beautiful bird. I had a cockatiel for 18 years named Bill. He may have lived longer had he not got blind in one eye due to an eye infection after giving him a bath. He also hated to take baths.
This was in 1973. At that time the vet had told us that you are not suppose to give cockatiels baths. I suggest that you ask Sunny's vet about giving him a bath. I remeber that during that time I had canaries who loved taking baths on their own. Maybe this species of birds are not suppose to be given baths.