If whatever I am writing requires two weeks of my time to complete, I have edited the early portions of the manuscript many times before I have finished. I have had many opportunities to see the manuscript with almost the objectivity of a stranger. That is many opportunities to find vagueness where I ought to find specific details. Become suspicious the moment the technical level of your manuscript appears to be declining. Go back to your research and see what it is that is lacking in your knowledge of the subject.
All writing requires research, and how-to writing requires the most thorough and detailed research.
The harsh truth is that the quality of your writing of such material can never be better than quality of the research you do on the subject. But you must learn to measure the adequacy of your research by measuring the adequacy of your knowledge. Think of research in terms of quality, as you think of writing. That is, research can be poor, mediocre, or great, and it takes great research to turn out a great how-to material.