Hi Sleepless nights,
Please don't beat yourself up, as you are only one of the many parents who is not aware of how much coaching is needed these days.
The Bucks tests have 21 question types, and you must use papers with all these types, like those advised by Sally-Anne and Patricia.
You can either use papers formatted like the real tests with most of the questions like The Tutors e-papers and CD2, or practice each type separately with something like CD1, or the IPS VR practice questions.
You can also have a look at The Tutors method and technique
http://www.elevenplusexams.co.uk/pdf/th ... hnique.pdf
that shows how to tackle each type.
You could use some of the free downloads
http://www.elevenplusexams.co.uk/revisi ... wnload.php
in order to get an idea of what works best for your daughters. You need to remember that the exams are on paper so it is best to do a few pen an paper tests just before.
Considering this late stage, I would follow Sally-Anne suggestion of concentrating mostly on the problems areas by using a mix of test papers and question type practice.
Best of luck