When you manage your own build you end up with a whole lot of tasks you can do an acceptable job of but not necessarily a professional one. In some cases that is perfectly ok and easily justified by the substantial amounts of money you can save.
When it comes to drafting, you really are much better off getting the job done professionally, no matter how small you think it is. I only had to make the mistake once to know I will never make it again. Using a service like Draftaway means you share the responsibility with them and are ideally placed to get the most out of your contractors with quality drafts. For a great drafting service visit http://draftaway.com.au