Can't speak for Manitoba but in Ontario early season upland hunting is tough. Leaves on the trees, hot weather, mountain bikers all make for a challenging hunt and long gaps between flushes. Nonetheless, success is possible. Hunt near summer food sources, berries and such. Birds will still be scattered as long as the food is scattered/varied/abundant. Move very slowly, and listen intently. Grouse do a lot more running when the cover is thick. Hunt flushed grouse, they usually don't fly too far so long as you don't put a cloud of lead behind em. Good luck, I love upland hunting regardless of my succes rate.
Patrick