I spent about a month's worth of evenings staring blankly at the pages of the Oxford manuals with eyes glazed over. Then the day before the exam I did a 8-hour marathon session with the Bristol question bank. In the end I got a pretty respectable pass.
If you want to gash it, spend a few days wth the Bristol question bank and you can pretty much guarantee a pass. Alternatively, learn it properly, the old fashioned way over a few weeks, and you'll have a much more thorough base of knowledge. Military training may help in other ATPL exams but not so in Air Law where the regulations are diferent.
I have to say studying ATPL Air Law was one of the most mind-numbingly dull things I have ever done. Enjoy!