Do you need to think/write quickly. Use the FAST method:
F - Face it. The job isn't going away. It isn't getting easier. You will never get a perfect inspiration. Face the task and start.
A - Act on it. Start thinking and writing. Just put your fingers on gthe keyboard and see what they do. The finger bone's connected to the brain bone.
S - Say whatever comes to mind as you begin. Don't edit yourself - at least not yet. There will be time for that later.
T - Terminate. Whatever you have when the time is up is what you have. Walk away and come back to it at another time. If it isn't obscene, riddiculous, or illegal, post it.
That is what I am doing right now. I had no idea what I was going to write 5 minutes ago. I made this up and I practiced it and I am going to click the SAVE button now and head out to my next appointment. I'll clean it up later. DAST - Face, Act, Say, Terminate.
Next Day: I came back and had about 7 corrections to make - NO BIG DEAL! I made them and will probably find more to make tomorrow.