Welcome to DC, Julie! There are some great recipes in the slow cooker section here.
I use a top round, bottom round, whatever is on sale, cut in big chunks, throw in some cream of something soup, a can of Rotel, maybe some dry onion soup mix, whatever veggies like carrots, onions, mushrooms and celery on the bottom, and slow cook away. It always falls apart, nice and tender.
There was some recent discussion on a similar problem here. I think the upshot was to not overcook, and maybe use some acidic ingredient like tomato product or vinegar. You don't need a lot.
To brown or not to brown is a personal preference, I don't brown, but it might give the meat a deeper flavor.
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