The author of this web content has spent years compiling their knowledge and experience in designing electronics into a comprehensive 300+ page book. The Table of Contents covers everything from planning and selecting components to troubleshooting and building a lab. They also provide tips on giving a demo and list companies that can help with the process. Surprisingly, the book is available for free as a digital copy or for $39 as a physical copy. Visit the website for more information and to download a copy.
https://www.hscott.net/designing-electronics-that-work/