There is a decent discussion (although it hopefully has been updated in the new edition) on using computer programs to create the drawings. There is a basic discussion for using CAD programs and the authors do provide the names of some programs to use. Hopefully, an updated edition will have a chapter about creating drawings using Visio (which is a program that many professionals use) and what software is better for different types of drawings than others. For example, some software programs are better for mechanical drawings and some programs are better for block diagrams.
The more you can do the drawings yourself, the more money you will save. Drawings tend to take a lot of time even for patent attorneys, and there are some drawings that even attorneys who like to do their own drawings have to send out to professional drafters. As I said in my review for Patent it Yourself, I would not begrudge anyone who wants to save money when trying to obtain a patent. It is a very long and expensive process even if you do it yourself. Likewise, I would not criticize anyone who makes the decision after reading Patent it Yourself that he or she does not want anything to do with tackling the patent process on their own. If you are going to try it yourself, I definitely think reading through this and the book Patent it Yourself is a good idea. Going through that material will, at the very least, give you an idea of what to expect and allow you to make an informed decision. And, if you do decide to hire a professional, the more you know about the process and can provide helpful input, the easier (and less expensive) the process is likely to be. And, the better drawings you can provide the professionals up front, the easier and less expensive the process tends to be.