You'll have to search, but there was a recent thread on this (last couple days).
Posters noted that you may get fewer smells if you use a permethrin concentrate that is NOT diluted with "other petroleum distillates" as noted on the bottle. Some were of the opinion that the sprays had better staying-power in clothing, because it was formulated to bond with fabric (this was speculation/anecdotal).
I've used the soak method with a concentrate with petroleum products making up the inactive ingredients, and it only had a faint odor after drying. I never washed them enough myself to determine if they had better or worse longevity than a spray.
That said, be VERY careful when handling the stuff, and look online for calculators that will get you the right concentration from whatever you are starting with. Concentration, the molar mass of permethrin itself, and simple arithmetic errors (0.5% vs decimal 0.005!) could be a waste, stink, or maybe make you sick.
Check your math and be immediately skeptical of anyone saying "dude, just dilute x into y and you're good to go"!