For instance, when he was blocked hard on the third volume in his space opera series, he just sat down one day and started writing stream of consciousness, letting the words pour out of him and not worrying about how well they did or didn't work. Several tens of thousands of words later, he had the makings of a military science fiction novel that became the first of another series. Another episode of blockage became the beginning of his new Western, playing in what is widely regarded as a moribund genre.
No one technique works for everyone. But as I used to tell students, every technique is a tool in your mental toolbox. The more you have available, the more likely you'll have one that works for your situation.