Althoug I worked on Bran's "Bette Noir" for almost five months I did not get to record many vocals with him. We mostly tracked and overdubbed a lot of different instrumentation. The few I did, Bryan definitely had a process. He would first vocalize various sounds over the backing track and keep only those that resonated with him. He would build up a library of those sounds and then start to write lyrics around them.
Sometimes that was a quick process and sometimes not. Whenever he felt comfortable
with his first draft, then he would sing those down and changes might be made immediately or upon futher rewrites. It was a long process , certainly one that I had seen before to some degree with Bono and Peter Gabriel. I never got to finish that record as I had commited to co-producing with Mr. Mister and had already pushed back the start of that by 6 weeks. When I left the project in January 1987 we joked that I would come back to mix the album when my production was finshed. Unfortunately for me and that record, Bryan did not complete Bette Noir until the summer of 1988 !
As I said before, sometime you have to wait for genius.