EGOL sir, you probably nailed it!
Whenever creating titles and descriptions you have to think about two areas
- Your search audience
- Search Engine Rankings
Id I would be at your place, I would list down all the important keywords in one document and then map the keywords on different pages of the website accordingly. Once done and I know what keywords I should be placing on each URL/page, I will move accordingly.
Once I have keywords mapped, next thing is to divide the pages as per the priorities. Important, Less Important and rest of the pages
Start with important pages, than move towards less important pages and then the pages that are on the website but not your priority at all.
As EGOL said, dedicate some time in your day may be half hour everyday (if you have another person to do the job in that case its different) and get the job done. This way it will be more efficient and closer to what your audience is looking for
Hope this helps!