When it comes to writing technical documentation, several skills and talents are required to produce successful results:
Attention to detail means noticing everything that might be important to at least some clients some of the time, capturing that information, then presenting it in a clear, complete, concise, accurate and precise way.
Accuracy means that the material is correct.
Precision means that everything is explained in detail, with no room for misinterpretation, missing out on a step etc.
Engineering design, software development and technical writing have many things in common - I've done all three. Everything on the list above applies to each of these endeavors.
Attention to detail is the foundation to producing a great manual.