This isn't quite sciency, but a bit more empirical. The few times I've dealt with pest control on my own, I've noticed that the instructions for chemical products discussed creating a perimeter around each room with them and laying the stuff down that way. Now, if you're not for using chemical pesticides, might as well quit here because that's what I'm referring to, but anyway, my point is that instead of trying to locate every crack and crevice, I've simply taken the horizontal planes (floor, countertops where those matter, and cabinet/closet shelves) and simply applied the pesticides there where the vertical and horizontal surfaces met (obviously I'm not talking about covering the entire surface, but merely laying a line down at those junctions). Eventually, the critters'll have to go horizontal, right? Well, at ever junction I could reach where I'd noticed them coming in, they'd run into the stuff I'd laid down and, if they survived, would track it back to their nest and kill off the nest.
It took a couple of years, but it was successful. Now I hardly have any insect invasions.
Again, this may not apply to you if you choose to avoid chemical pesticides, but my overall point is that I noticed that practical application suggestions were to create virtual perimeters in the rooms. This in contrast to attacking each entry point. That's what I was getting at. And the suggestions felt very much like they were informed by experience. It sounds like it's harder, but it actually was not, at least not for me. I wasn't crawling around each and every area looking for minute places and laid the protection down pretty fast.