With ants and other ground crawlers, here’s the “trick” I usually don’t see people trying - but it has worked well for me. You need PATIENCE - and a little focus - maybe wait til you’re the last one left. Then…WATCH AND FOLLOW THEM. Find out where they get in and out, and close it off.
There’s going to be a path or two. Ants, you’ll see them coming in empty handed, and leaving with a little crumb or something. Just follow them along, and see where it is they enter your place.
Sure, they’ll probably eventually find another way - but you can effectively stop them for a while.
I found two little, teeny holes in my FLOOR - which is actually the building slab - stained and sealed. Ants had found it - I guess tunneling underground to it. I just re-seal that spot (yes, I poured some clearcoat into a hold and subjected some ants to a gruesome sticky death) - and poof, no more ants.
Some other little critters were getting through an exterior wall with a linoleum cove base directly into restrooms. The access was a gap at the top of the cove. Me and my trusty caulk gun with some silicone solved that one.
Much more effective, and cost efficient than “spraying” the whole building…
Shotgun will hit more targets than a rifle . . . sure we have toxins flying all over the place . … but hey.