I've been told that the main impediment to speed-reading is subvocalization - pronouncing the words in your head, as you read them. If you can stop subvocalizing, you're capable of extracting concepts from text much faster.
Learning to speed-read might be a useful step towards your goal. Apply the usual second-hand disclaimers: I haven't tried this myself.
Before language, people must have thought without words. I often have the impression that I have a thought fully-formed in my head, yet I wait to listen to it unfold in words before moving on to the next thought. Perhaps I could think much faster if I weren't addicted to words.
Has anyone developed techniques for thinking without words?
This would have a little in common with Buddhist practices of emptying your mind, but wouldn't be the same thing. For one thing, Buddhists also try to empty their minds of images. More importantly, they are trying not to think, while I'm trying to think - just not unpack everything into words.