On top of that, while you can usually submit the same resume you spent hours tweaking to similar jobs, the same can't be said for cover letters. Each new job posting will likely require the patient — and potentially heart-wrenching — labor of crafting a new letter.
If you want expert advice and guidance on how to create the kind of cover letter that gets pulled to the top of the pile, you might want to invest a little time into a cheap online course. Some are taught by HR veterans and professors who can tailor your application to perform well with screening software, and while it can seem like a bit of a time commitment, you'll at least know for certain that your approach to applying for jobs is the right one (over hours spent pouring over Google search results).