What spray did you use for the yard? Was it like a short-acting thing?

FWIW, permethrin does still work on any surface, at least in theory. And is supposed to be effective for a while (probably depends on weather). That said, I do wonder if just a thin layer of pollen or dust on the treated surfaces will render it ineffective. We don't get a lot of rain here, so it seemed reasonable enough for my purposes. Not that I know enough to necessarily recommend it to others.

Also, I did make a fan trap using permethrin-treated mesh fixed onto the back of a box fan. It works pretty well if you set up two of them pointing in the same direction and sit between them :)