Not all training is created equal. When I hear that "I've tried training my co-workers, but nothing seems to help!" My first question is, "Can I see what your training looks like?"
A quick look at a slide deck, and it's easy to see why training isn't going so well. Most slide decks include information meant for awareness, not training. After spending four hours in a classroom, your co-workers are aware they use Salesforce. They are aware of Global Search and objects. And they are aware that they are supposed to use Salesforce to do their job.
But your co-workers leave training without a clear idea of what their job is, where to do their job, or how to do their job.