You can't be expected to know everything off the top of your head...but maybe about a third to a half of the questions are general electrical knowledge, so the correct answer should be pretty obvious. You can fly through these.
Through experience you may know the maximum Zs for 6A and 32A Type B breakers. That might save you 2 minutes if they asked you about those.
Some will require looking up and to help you I will give you three page numbers: 48, 49 and 164.
48 and 49 are tables of maximum loop impedances for 0.4 and 5 second disconnection times. Write "5 SECONDS" in red in the right hand margin alongside table 41.4, so you don't confuse it with the values for 0.4 seconds in table 41.2 on page 48.
Page 164 is the index of Special Locations.
Go through all the ones you know off the top of your head first, flagging the ones you'll need to look up and coming back to them later.
The questions tend to be in the order from front to back of the book, except for the special locations ones which are thrown in at random.
So if you're really stuck on one, you will have a clue about which part of the book to look in.
I flew through mine, then spent 45 minutes looking for one answer at the end... and still chose the wrong answer for it. But it was the only one I got wrong
Simon.