I've never done anything resembling professional writing, but I've always found myself creatively paralyzed when sitting in front of a keyboard. Not quite sure why, but it's so much easier to let it all flow out with a pencil and paper.
That can definitely help! I do work with some students who have learning challenges or other issues with writing, physical or otherwise, for whom writing by hand isn't an option. Freewriting is a good idea whether by pencil or by keyboard, though!