If you ask me, I'd say that the best way to learn is by practising the problems. Through practice, I was able to learn and use strategies more efficiently than by just reading about strategies. I found the strategies in the
MGMAT IR book all boiled down to common sense such as read the questions properly, ask yourself the right questions etc. and it didn't help me much at all. If you already have the
MGMAT QBanks, I'd say stick with finding strategies through free online resources. If you've seen the
MGMAT IR workshop, its basically covers everything in the book anyway.