Good to hear about a few bruins being seen, keep in mind that far and away the best time is still to come..
As far as calls go, I'm absolutely convinced that most any call will do on any given day. You just need to find a tone, cadence, volume level etc that makes that bruin up and come in. Like I mentioned B4 about a third of them will pay you no freaking attention. I've been within 75 yards of a bruin and just howling on a call and the bear didn't look at me once! Heck I even used a peacock call once just to see if I could call in a bruin, and it worked (on at least one bear).
This is just one of the main reasons I like to watch the bruin (if possible) is that I can change things up until he gets to moving or I decide he's just not going to play ball.
Another thing is I go full tilt whaling on the call as hard as I can from the get go and I don't let up unless I want him to slow down so a shot can be taken (this can work well for archers). IE. once they break 50 yds just shut up and more than likely he'll go into sneak mode and hunt for you. Kind of like your lab working a pheasant.
I normally hunt alone or with my wife or one of my grandkids but when being serious about calling bruins I don't mind having another person along as then we can set up watching different directions as well you have a second set of lungs to keep calling and to keep the noise going as often when the calling ceases they loose interest fast. Then you have to get them going again.
I like to call for 30 minutes on the short end and 45 on the long. Just like calling yotes often times you won't know that they're working you until right at the end so don't be quick to give up.
I watched a couple you tube vids the other day and hunters would say like hmm I think I'm going to try calling, they sit down, make a couple of toots and say something like hmm no bears around I guess or this calling stuff really doesn't work. If only they really knew eh
Please keep in mind for me it's the making a critter come to me that I love and the closer the better (5 yards is my closest so far), shooting them isn't that high on my list anymore (old fart I guess). Point being often times I call on bears that a good rifleman could easy sit down and take out if they so choose. Different strokes I guess, so get out there and work on calling in a bruin.