Another method of idea generation is to produce a lot of ideas. Think of a conveyor belt or a luggage carousel, endlessly moving and bringing forth one object after another. The idea that's coming down the conveyor belt right now may not be the one you need, but the next one might be.
Pushing yourself to keep the ideas coming is a way to keep the creativity channel moving and to reduce the pressure of thinking that every idea has to be 'the one.'
Writing teacher Natalie Goldberg tells her students to keep the hand moving across the page, even if you're just writing 'I can't think of anything new to say.' Ideas lead to more ideas, which lead to even more ideas. You have to get the 'bad' ideas out of the way, so that the 'good' ones can emerge.
Thomas Edison, when he wasn't pondering how pinecones grow upside down, produced one minor invention every ten days and a major invention every six months. He still holds the record for number of patents: 1,093.