None of the exams are difficult, you just need the commitment to learn the syllabus. A full set of Thom or Pratt books, together with the confuser will get you through.
It is possible to pass the exams with the confuser alone, but your knowledge would be limited, & I wouldn't recommend it. Dont forget the examiner may also throw a couple of questions at you during your skills test, so dont just cram for the written exams then erase all from memory!