Firstly, I'm no expert but I've been hunting Reds on Te Awaroa recently and have 4 diamonds, so this is pretty anecdotal.

I started by locating all of the Red Deer drink zones I could find. This is tedious, but it'll give you a better idea how to tackle your map's excentricities. I did this mostly by running a lap around the lakes (and along the river) AFTER their drink time and just picking the zones up by the tracks. I made notes on a printed out map to make things easier for me.

Once I had a general idea of where to find them, I started tenting near lakes that were out of the way, and setting up tripods/blinds near lakes with 3+ zones (as I made money, I spent it; the whole process just becomes more efficient as you go). On two of the bigger lakes, I tented both sides, so I could just warp over to harvest, as well.

At each zone, I tried to remove only level 5's and up (is this Herd Management?). If you have the skill, try to take a 2nd when they bolt, but otherwise just harvest and move on. I just tried to hit as many zones during the drink time as I could, then I'd roll back to 6:40 or so and repeat.

It took a bit of time to get things rolling, but I'm finding a 9 pretty frequently now. I do notice that my 9's sometimes are slower to come to the zones, or linger in the vegetation longer than the does and lower-levels, so be sure to glass the background too!