The passive voice of the pluperfect tense seems to be a careful combination of the perfect passive and the pluperfect active. It's quick, easy, and painless, especially if you know your theory of tenses. (N.B., much of this video may seem familiar to you if you already know the perfect passive - but that's by design, since it's just a small flick of the wrist to change from one to the other)
indicative mood passive voice verbs