Take the detour south at Medicine Hat on HW41. Elkwater is your town for supplies and a nice lake. Continue south to TWP74 (there are a few options heading east), easy enough to figure out and get to Ft Walsh which has some good hiking trails where we saw lots of wildlife like moose and deer. Place has a some interesting dark history(massacre) if you have time for the visitor centre, worth doing before you hit the trials so you know where the blood piles are.
We were staying in Elkwater so headed back there, but I'm sure there is more neat stuff heading back up to the TCH. Really cool area. Oh, I'd try to time it for mid-week, Elkwater gets a bit busy on weekends and it is so nice when no one is around.
EDIT: some pics
Spoiler!
Elkwater:
Stormy skies are incredible.
Drive to Ft Walsh:
Ft Walsh area