Had Been Kullanımı. However you can use had been in indirect speech. These two sentences are equivalent for example.

I am sure he can give us some advice about where to eat or where to stay. I may have been taking a shower when you called. Answer 1 of 2.
How long have you been painting the.
We dont usually use a continuous tense with wish in this case. However you can use had been in indirect speech. I have not come across any sentence in english with had had been. This is very formal.