I don't think following a style guide is overkill. It's really helpful to have an authoritative answer to things like whether to use e-mail or email and not have to look them up a dozen times or argue over them with other people. However, CMOS is probably too detailed for your needs, and I certainly wouldn't read it cover to cover. Even as someone whose whole job is writing, I wouldn't sit and read a style guide from front to back. For an electrical engineer, I don't think that's a good use of your time.
Currently on my bookshelf, I have The AP Stylebook and The Microsoft Manual of Style. I like both, although AP doesn't use serial commas and I personally like serial commas. Microsoft is really helpful for software instructions because it defines how to format button, window, screen, and menu names.
It might actually be more useful to write up your own style guide and create a template for the documents you write most. The style guide can be a simple list of style decisions; it doesn't need to include everything under the sun. When I write user manuals, I list all the parts of the interface and how to style those terms. (For example, if the application has a small 3D map for navigation, I note whether it's called the Mini Map, the Mini-Map, the 3D Map, the Navigation Map, or whatever.) I also include any terms that come up that have more than one standard spelling or hyphenation. Every time I have a question about a term when I'm writing or editing, once I resolve it, I add it to the list.
You can use that style guide just for yourself or, depending on how much pull you have and how much your organization cares about writing consistency, share it with the rest of your team.
IEEE Standards are a good resource for developing templates, because their standard for a given document usually includes a sample outline and a description of the content for each section. It's generally not too hard to set up a Word document with the specific formatting you want, the sections all laid out, and comments indicating what should actually go in those sections.