Because every student is different, advising students with impairments in matters of writing requires innovation. As with all writers, what works for one student will not necessarily work for another. Accordingly, we cannot, via the web, offer a "plan" (or even a group of plans) that will transform students into competent writers. What we can offer is some anecdotal advice, gathered over the years from students who have used these strategies to become clearer, more efficient writers.
First, we should acknowledge that students with impairments benefit from the strategies that we offer throughout this site. Good practice is good practice. And so perhaps the most important step in taking control of your writing process is to make that process as concrete as you possibly can. The writing process typically involves several steps: coming up with a topic, developing a thesis, organizing your thoughts, writing and rewriting, refining your sentences, and correcting your grammar. You should never try to rush this process. Don't skip steps; don't try to write "straight from your head."
Instead, make the process concrete. Write everything down. When you are coming up with a topic for your paper, brainstorm by making a list of every idea that comes into your head. Once you have a list, look at your ideas and try to sketch them, using arrows or colored markers to cluster your ideas so that you can easily see which seem to go together. You might want to go even further and annotate each of your clusters. In other words, write a sentence or two that suggests how these ideas relate to one another.
If making lists doesn't work for you, try freewriting. And if freewriting feels too random, try to write a more focused discovery draft. You may, in fact, want to write more than one. Tip: the more writing you do when you are planning the paper, the more you'll have to work with when you start to write.
Once you've come up with your topic, you'll want to develop a working thesis sentence. Learning-disabled students might profit by writing a thesis sentence that has an explicit essay map. This map will direct you through the major points of your paper and can prevent you from getting lost in tangential ideas. (For more information about developing the thesis statement, see Developing Your Ideas and Finding Your Thesis.)
Use your essay map to suggest a structure for your paper. Make a detailed outline to help you to develop your idea logically. Tip: Outlines should be fluid. As your ideas evolve, so do your outlines. Try to keep your outline current with your evolving ideas.
One final way of making the writing process more concrete is to keep notes about where and when you are having trouble with a paper. For example, if you are having trouble keeping your second point separate from your third point, make a note of that. Later, when you are revising your paper, check your process notes and make sure that you've addressed the problems that arose while you were writing.