If there’s a part bogging me down, I try to leap over it, somehow, and see if the piece will work without it. (It usually does.)
And not just skip the boring parts: rethink them. If it’s boring, think of what would make it more interesting.
“Often as not, I would remember some aspect of the subject that deeply interested me, something a little outside the way it’s usually perceived or written about. Then I would meditate on that, and soon I would be scribbling notes from an increasingly excited place until I found a way forward.”