A priest friend asked me if I knew of some good catechetical material to teach about 'ad orientem' worship. Maybe you might be able to help him out in the 'comments box'.
For us the transition from 'contra populum' to 'ad orientem' was relatively easy as it happened in 2009 just after the publication of Summorum Pontificum. The great advantage we had was because of our restoration work we had no sanctuary floor for almost three months, the only sensible option was to celebrate Mass facing East in the narrow space between the pews and the sanctuary. In fact when the boards were laid and we did return to facing the people there seemed a general sense that East was best and at that time was the mind of the Pope, as it had been up until the late sixties the mind of the Church. Very occasionally, like once or twice a year, a visitor of which we have many might express surprise at the orientation of our worship, though the normal, almost weekly comment, is about the beauty of the Mass and the quality of our music.
We did do some catechesis, for Lent we, those took a significant role in parish liturgy studied Benedict's Spirit of the Liturgy but the for the majority of the congregation what convinced them was not catechesis but the actual experience that 'ad orientem' was obviously right and fitting.