The daydreaming is the most under looked part of the work. Its actually the birthday of the vision. To me it's not a romanticised process in any way. No, no, no! It's a time you have to plan for yourself and have to put it in the schedule as you schedule your meetings. You have to ensure conditions of pure leisure and undisturbed focus. I have heard an alternative wording for it, a deep work - a state of an absolute concentration.
When I was a kid I discovered a technique that still works for me - its a bridge that unlocks a free flow of ideas. You stand up from your desk and begin to walk around the room. Talk to your self, make an interview with yourself, describe your work, explain it to others and soon you will not be able to stop. Change your clothes - put your suit on, wear your beach slippers, see how your voice change. Then its just a matter of sitting down and writing notes. Notes can be messy as the free flow is. If you are not happy about your direction of ideas, then change it to the opposite way. Maybe you needed a stream to fight against. Then its just a matter of time until someone knocks on your door and wakes you up.