Guist gets a lot of pressure, so downsizing usually helps me. Small crankbaits, spinners, 4" worms if the water's clear.
I don't see too many people fishing C-rigs on Guist, so that's a fair choice if it's tough. Which is often.
The best "inside" tip I could give you on Guist is that most people buzz right through the marina no-wake area and there are always some fish in there.
"60 wall" is probably the best known place for big fish. There's another good deep bank with cover across the lake from 60 wall and about 1/4 mile closer to the dam.
If it's rainy watch for schooling fish. Good luck.