I'm curious how they'd toughen the course just for the tour event? Was it things like changing the size/position of hazards or were there more subtle differences?
1. Move the holes on the green. It's pretty easy to do, you basically have a giant cookie cutter that cuts a hole out, you drop in a cup and then move the bit you cut out into the old hole. On a well maintained course the seam will be gone in a few days. Most courses have a map of where the possible hole positions and a difficulty measure for each configuration.
2. Watering/not watering greens. If you don't water for a few days, the greens get harder and the ball doesn't slow down very much. On a sloped green this can make a decent landing turn into a gigantic overshoot.
3. Mowing height. A tall rough can suck energy out of your swing. A low green makes the ball roll fast. I'm not sure if they change the height for all areas of the course (especially if you're happy with your greens), but it seems trivial to let the rough get a little higher.
In your comment you mention moving the size/position of hazards. Moving bunkers is a bit of an ordeal and I'm not sure if they would do that for a PGA tour (but I could be wrong). Making the water level higher so the ponds get bigger seems easy enough though.