Self study is definitely possible and you should be able to bounce questions off a range of sources such as BT or your instructor etc.
Unlike the smarter folks above it took me 8 months although i was working fulltime in a business role that had me occupied 12-15hrs a day, 6 days a week. Pretty hard trying to study at 9pm after being at work with your head in spreadsheets all day! Nevertheless managed to get them all on first go with some good results.
A word of warning with BT though, he will teach you enough to get through the exam and pass but there are sections that he breezes through without much detail and these can sometimes catch you out in exams if they are questioned in depth.
Good luck with it all!