I've played piano for many years but I'd like to do some work on my technique and am going to attack the Hanon exercises.  I have a very simple question on the instructions though.   You are instructed to play each exercise initially slow (eg at 60bpm) moving up to fast (eg at 108bpm).  Can you please tell me whether the book is intending for you to master the entire first part (20 exercises) at 60bpm before increasing the tempo, or whether you are supposed to master each exercise up to fast before going on to the next?   I've read the instructions several several but can't decide which it means!   I think I could make a good argument for doing either, but I'd rather stick to what is best practice.

Thank you =)

Phil