No no no no to Excel. This is how you spec quarterly reports, not products.
I personally create a tech package, using Illustrator, and saving all the files into one multi-page PDF. This PDF contains drawings, material call outs, construction/manufacturing information, sometimes a page of pure text (etc, etc, etc). This way it, more or less, can’t be edited by anyone who sees fit, and I know the client, factory manager, and workers in the prototyping rooms will all see the same thing. That’s my method, I’ve seen many others use this method too (seems to be industry standard for my specific industry). But I’m sure there are many others out there.
In my opinion, using Excel would make me feel less professional, and make me think my clients would also feel this way about me. You’re being hired to do things that your client cannot do. So I feel like using a program that your client is probably an expert at, makes you less credible. We should use programs that are more powerful than accounting programs for Industrial Design. Just my two cents.
Best of luck!