I found myself to be in the same position. Although I haven't given the actual test but after a couple of diagnostic tests I found myself weak in RC and SC (ironically I'm from Canada too).

I strongly recommend the MGMAT guides (for SC and RC). Although you need to be at a certain level before, the guides certainly help break down the test and help identify weaknesses within a section e.g. SC. I found myself weak in parallelism and modifiers.

For SC I suggest going through each chapter, doing the OG Q's at the end of the chapter. I used to do all questions from one chapter and then go back and look at answers. I suggest doing one question at a time i.e. solve the question, read answer to determine why you got it wrong, were you able to narrow down to two or three choices, what is wrong with the answer choices and make notes. I starting to see some improvements with this method.

I haven't got to RC yet so I can't advise there.