Thank you for the reply. I am sorry for the delay, but I did not see that you had responded until now.
Looking up the product, I see that it does contain a permethrin, which cats do not tolerate well at all when used in higher concentrations topically, but the concentration of the premise spray is fairly low and if you waited to let it dry before allowing exposure, it would seem odd it would be from that. That being said, his reaction does sound like a mild version of the a flea product toxicity. Of course, there are other causes of drooling in cats which can include nausea or other GI upset, dental problems, or trauma, but the dilated pupils makes me think it is more likely chemical related.
As long as there are no breathing problems, tremors or seizures, it should be OK monitor at this point, especially since it sounds as if things may be getting better. I would looks around the house to make sure there is no evidence that he may have gotten into something else. I would also wash his feet in case he stepped in an area that may have had residual dried spray and then licked. it. You can administer benedryl, but giving oral liquid meds to a cat may exacerbate the drooling, just because they don't like it (especially if he didn't like you wiping his mouth).
I would keep a close eye on him and if any of his symptoms appear to be progressing instead of resolving, I would have him evaluated by your vet.
I hope this is helpful. Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please reply so I can clarify for you.
My posted replies are for general education only and not meant as a diagnosis. Only after a thorough veterinary examination can a diagnosis for your pet be made and specific treatments be advised or medications be prescribed.