I have been messing about with this. Writing shorts with a long one in progress. Then I find that I cannibalize the ideas from the short stories into the long. I also rewrite, sometimes almost totally. The whole thing ends up a little confusing but it has some advantages. Firstly I decided long ago to overlap characters between stories and this method keeps the kettle boiling. Secondly I get ideas that at first do not fit and write a short story (perhaps 1000-2000 words) and then realise a way of melding it with the novel length ones. It must all sound a bit haphazard but it works for me.
I keep a text file of notes that include situations and ideas that I have dreamed up, read about or seen in pictures. Plots from soaps, films and TV can provide inspiration for plotting structure or character development. I enlarge these in the text file until they reach a detail level that means that they are no longer a set of bullet points or list but become a separate piece of prose. These then get picked up. I reckon I've thrown more away than I have used but when I am feeling creative ideas are better than prose and the other way round.
The biggest drawback is continuety because it requires constant re-reading to continue and find a thread. The up side is that the re reading exposes the text to continual checking.