How long really depends on how dirty the car is. I'd say a once over would take 25-35 minutes. Then go back to each area and see what you missed. I try to do a lot of cleaning the night before the show and then only have to get what I picked up driving.
As far as where to put everything. I just posted this pic in "the detail shop" section of this forum about a bag I picked up on eBay for just a few bucks. Holds everything I need and I tend to take a lot with me to each show. A desent size bucket will hold a lot too.
