From my limited experence I can offer this.
The sound of them eating can be reproduced by rubbing 2 quarters together.
I never look directly at them unless it's through a scope or binos. They don't seem to get spooked then.
Find the right trees they're feeding on, walk looking for piles of nut shells, sit and wait, or proceed very slowly. They come out and start chattering at you.
I like the rock idea, obvious now I know it! Thanks.