I used, for PPL, the Thom books, supplemented by some older texts, like the Alan Bramson book which used to be used for the UK PPL.
Though I work some of the time in the IT industry, I find CBT very limiting, since it does not allow easily for followup of lines of thought which arise on the spur of the moment, and which are out of sequence for the order presented in the CBT.
Persoanlly, I cannot see the point in the Confuser or other quiz-type facilities, there was more than sufficient in the Thom books to gain an idea of one's retention and understanding. It is all striaghtforward anyway.