As Trinity Sunday approaches I am reminded of a story told to me about something that occurred in one of our (APA) parishes a while back. A woman and her daughter from a non-denominational church wanted to join this parish. As they were not confirmed a lay leader in the church worked with them to prepare them for confirmation. Somewhere along the line this lay leader had acquired a confirmation catechism that had been created for use in another parish by a learned and devout priest. So that is what she used to prepare these people for confirmation.
Everything was going fine until they got to the section on the Holy Trinity. Following St. Augustine, the booklet - without any explanation - said that the Holy Ghost is the "love between the Father and the Son." When the catechumen read this she questioned the lay leader: "Where is that in the Bible?" The lay leader was stumped and could not provide an answer! This "strange teaching" immediately became a major issue for these people. I never heard what happened after that, but I presume any confusion was eventually cleared up, and the people were eventually confirmed and received into the parish.
The thing I took away from hearing all of this is that it is probably best to avoid using home grown confirmation material such as this lay leader was using, as there is no telling what is in them, how orthodox they are, or quite simply if they are even appropriate. In this case, while the material itself was undoubtedly orthodox it was probably too "high level" for these new members, and thus inappropriate. In my opinion clergy and lay leaders would do best to stick with the tried and true material in the Book of Common Prayer, namely the Offices of Instruction and Catechism, for preparing folk for confirmation. This material is staright-forward, simple, and too-the-point and focuses on the essentials of the catholic faith.