Writing a dissertation is simply very time-consuming. So brace yourself and take every help that you can to write your dissertation in a reasonable amount of time. If you have already published a paper then make sure to include that as a chapter in your dissertation. As you carry on doing experiments or case studies, evaluate results – even failed experiments are valuable because they can provide fodder for evaluation and discussion in your dissertation. You don't necessarily have to wait until the last moment to write the literature review, in fact, the sooner you get on with it the better it is for you. And in order to help you save time, it is handy to have annotated bibliographies. Also, you can start writing the methodologies and techniques sections as soon as you start to run your experiments or carry on with your case studies.
Additionally, you must gather all the writings that you have done when presenting your work at national or international conferences. As you present your work at different workshops, less formal lab group meetings, committee meetings, graduate student conferences and so on, you should have accumulated content from participating in those events. Repurpose that content in your final dissertation writing.
It is very practical and productive to join a peer dissertation writing group. Graduate students sharing the common experience can meet at mutually agreeable times and discuss the bottleneck in their writing process, and also strategize and discuss the smart tips of writing quickly. Additionally, the meetings will help you set realistic deadlines and take the help of your peers to get additional layers of revision and proofreading. Also as you finish writing each chapter share it with your mentor. Get their feedback, this will help you to make quick revisions and save you time in the long run. You mentor will not only proofread the documents but also give valuable feedback on the subject matter itself. Revising the whole chunk of writing can be an arduous and intimidating process.