That lake is gin clear!!! The best walleye fishing is at night, but the park closes at dusk,...so unless you know somebody, you'll have to be off the water before dark!
Troll deep diving rapala's or other "body baits" and live-bait rigs along the drop offs and in front of the beach....fish deep though!! You could even try a 3-way rig and bottom bouncer for more direct control of your presentation. Another really good walleye lake is Union Lk. It's full of 'eyes and you can get them on jerk baits around the drop offs and sunken islands!
Good luck,....and "Fire Tiger or perch" patterns are good colors for both lakes!! (for the 'eyes)
if you have a map of cass, find wards point. if you dont have a map, go out the main lake and then cut to the left and go all the way back. you cant miss it. theres a big house and a fenced yard all around the point. fish the back side of that point just as the sun is going down with suspending jerkbaits. doesnt really seem to matter what kind. i am a big rogue fan, but my friends catch them on husky jerks, thundersticks, bombers, etc.
we load up on the eyes out there this time of year. you will rish getting locked in the park. we got locked in there one night and had to tow the big rock out of the way to get out. wasnt pretty.
You can get some walleyes over the weed beds along the edges in a good breeze too. I caught a 20 inch walleye near Wards Pt on a jerkbait in 6 to 8 feet of water over sparse weeds near the drop mid-afternoon with a brisk breeze blowing in.
I've caught most on main lake edges near weed beds on overcast/dark days, but I caught a nice one once on a topwater in the Guts about 1pm a 100 yards to the right of the boat ramp.