Imo the best thing to do is to play this game in amongst others and not solely focus on it. The course mastery is really boring. Playing round after round is tiresome so do a couple of rounds on your career and then play another game and come back.
Beware that on some courses (I forget which) there are only two Par 5s, this means getting the 5 eagles can be tricky or is overlooked. Bear this in mind so you don't have to play a full round just to get 1 eagle.
My PSN is ~ Larsen_Bee
Toughest Platinum: Wipeout HD
Toughest PSN 100%: The Last Guy