Alex is pretty much spot on. BM can be time consuming but if you're smart about it, you can merely "cram" it and do well. By cram it shouldn't mean that you leave it till the very last minute. What I did was ensure that when writing my notes, they were concise but also not just mind numblingly copied out of the book because that pretty much means you don't remember them and waste time writing notes which are as thick as the text book.
Be smart about your notes and cover everything.
For the exam, you don't necessarily need to do endless practice exams beforehand, just make sure you know what is required of you and how marks are allocated. I did 1 trial exam before the real thing (which was the previous year's VCAA) and I ended up with a 49.
Cramming will only take you so far though, the area where a lot of students lose out is when they dont properly answer the question and spout off a simple rote learnt definition when the question asks for more.
BM can be as time consuming as you make it. If you work well on notes and understand what is needed, then you can save yourself plenty of time. Good luck!