Aha, you are working the West Branch! Yep, brookie country, tight casting, narrow shooting lanes...the whole deal. I actually did most of my fishing on the mainstem below Lake Kathleen. There was (is?) an access about 1/2-3/4 miles south of the Brutus Road Bridge (another spot I've fished), we used to call it "behind the Indians" during my U of M Bio Station days (1984-1990) - west side of the road, two-track. It's state forest land, and they had a big sand trap dug out in there, but that stretch still holds some nice fish, including an 11" brookie back in 2010. In fact, all three species are abundant in that water, so a "Michigan Grand Slam" is not all that uncommon (did my first waaaay back in 1990). This area is where I have by far the most experience on that river, but I would think hatches and etc. aren't too much different except for the colder temps in the WB. (The East Branch feeds out of the west end of Douglas Lake, opposite side of the lake from the Bio station and so it's warm surface waters that do eventfully get some cooling from groundwater inputs. It's plenty cold by the time you get to the Mainstem.)
Hendricksons right now, Light Cahills into June and July, Hex sporadic in Late June and early July. Go to Hoppe's Bar on Burt Lake, when the Hex show up all over the building you can bet it's about one week before they come out the river. I tie size 6-8 extended body elkhair imitations with flared (spent) wings, can also tie some with upright wings for emerging duns. For the Light Cahills, a #`12 White Wulff works very well. A Royal Wulff in the same size or #10 makes an excellent attractor fly. There are some grassy stretches in there so be sure to have some hoppers and crickets late in the season! Right now it's Hennies, Red quills, and caddis, with some dark Woollies thrown in for good measure. Good luck!! And pretty brookie, that place grows some handsome fish.
Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...