I've just spent 2 lessons going over the mock paper (2 x 50 minutes).
Rather than going over it in a linear way, I put the students into trios and had them produce "perfect answers" against the assessment objectives in the answer scheme. Students had the opportunity to double check and talk to other teams, a few did.
The process allowed students to share patterns of answers, and even the more able were able to see where the construction of their answers, despite obvious knowledge, didn't score all the marks available.
The obvious extension of this is to get them to write the answer scheme, which I think I'll get them to do...