I co-wrote a border search guide for EFF some years ago. I was very interested in finding clever technical approaches but I later ended up feeling that I hadn't given enough thought to the overall threat model questions (even though the guide did address them, perhaps even somewhat usefully). The big picture problem is that the agents performing the searches have an enormous amount of power in terms of potentially se…
Perhaps your friendly smiling Yes-Sir-No-Sir-3-bags-Full-Sir act might just be enough to let you get on your way without anything else happening apart from a stamp in your passport.
Even the slightest hint of defiance or surliness from you to a border guard/policeman/etc - potentially at the end of a long shift, tired, angry, pissed-off or whatever - and you're straight away hugely more likely to have a bad day.
Finding strategies to "beat the system" will, I think, just be a shortcut to some other punishment/crime/taken-out-of-sight-and-given-a-proper-kicking-oh-they-resisted-and-went-for-my-gun/etc as this person found out the hard way by trying to be difficult.
I genuinely don't think there is a "get out of jail free card" or magic incantation you can say to get out of these situations apart from just smiling and being polite and not being a dick - if you get into a "who can be more annoying" competition, then the border guards/police will always win since they hold all the cards and will happily ruin your day/holiday/meetings etc by detaining you (its their job to do this after all)
There have been cases very recently in the US where the authority figures down dealing with the public are evidently in a very defensive, aggressive "us-vs-them" mindset, with an itchy trigger-finger to go with it. Don't be the person on the receiving end of a cop seeing-red because you're being a jerk.
The house always wins.