We've talked to our "Orkin" guy about this, at times in our house...
Spiders are hard to get, the insecticide has to touch the spiders, because unlike other bugs, spiders dont lick thier feet like other insects do, so what usually kills spiders is the bug they ate, recently licked its feet, after going through whatever chem you laid out for them.
Bug bombs were discussed, as well as dilligent manual killings. BTW, if you bomb, you need to empty trailer of EVERYTHING, OPEN EVERY DOOR AND DRAWER (I excluded the fridge since they were not in there), you might need to tape around the bottom of top and top of bottom of Hilo, to get a better seal, so bomb will saturate into behind cabinets instead of leaking out places! you may have to try to spot spray in places like behind fridge and other places where they can hang out...
ALso do only set one off, after you make sure ANY source of flame or spark is turned off! let is sit overnight sealed up (best if locked of course so you dont kill any idiot that tries to sneek in) then air out next day
Another bet is sticky traps, lots of them, to start thinning the heards, I have a feeling, you might need to store in different place when you them cut down, and gone.
go around underneath your camper and fill entry points with that expanding foam, while you are under there, kill any spyders while there as well.