Last year when I was out there OnX wouldn't let me view it on my downloaded maps for some reason, but Maybe it's changed now. I found myself using SDGF phone app just as much as OnX.
I would have to agree with redman. The week before rifle is a good time to go but definitely not a deal breaker. Also from my experience the walk in areas hold more deer than most of the BLM land. It's a fun hunt and you should see a pile of deer. Not to mention nice big whitetail to look at on...
I have never been antelope hunting but my Grandpa used to go alot. I remember him telling me not to get upset if you see one and it takes off because there's a good chance it or another one will end up coming through that area again. Not sure if there's any truth to that but it's one theory lol.
Most of my buddies are the same way and it's kind of a bummer but I understand that not everyone has the same desire to do these kinds of things. I usually plan to go on a hunt Solo but sometimes I can get one of my friends to tag along. As fun as it just to be out hunting and taking a break...
Just do your research, know the public boundaries and enjoy your time in the field. I can't speak for Montana but you'll see plenty of deer in that part of South Dakota. Locals can be pretty helpful if you get a chance to chat and don't dismiss the small parcels of public. You'll have a great...