I was working in the area last week and hiked up the Whistler Canyon Trail (there is a well marked trailhead just south of Oroville) and then cut across the SW face of MT Hull to photograph sheep. Spotted 45 ewes with 13 lambs. Didn't see any rams this time. Also spent a good deal of time glassing from HWY97 and along Swanson Mill Rd. You can spot ewes pretty quick. I usually see them hanging out above and south of the gravel pit from June through August. Not sure if they stay in that area in the fall though.
I believe that access from below is fairly limited by private property, you can access via Whistler Canyon Trail on the northwest end, or from the top via Summit Lake Rd. Folks who live in the area can probably suggest contacts that may let you hike through private property to get up on the hill.
I'm curious what size rams people have seen in the area and which areas they tend to hang out in? I'd like to get some photographs of the rams but generally see only ewes. Do the rams head up top into the timber in the summer months or remain on the SW open face along the highway?
I'll try to attach a couple pics of ewes from last week. Feel free to pm me and I can give you a map/directions to areas they tend to hang out.
Good luck, should be a really fun hunt!