Giant Growth is best used during the declare blockers step when, after your opponent has declared who blocks this round and you receive priority again to play spells or abilities, you squeeze in the 3 damage to win the match with your Giant Growth.
Another thing the course does very well which is chronically hard to do is to play fairly for all abilities: less skilled players will love the generous corridors, while better golfers will be daunted by the prodigious length from the back tees, at 7, 269 yards.