I prefer the metaphorical ‘slap’ of a kaon and paradox too the physical one 🙂
I read to many personal accounts where the physical  ‘slaps’ intention was lost, a case where a method was confused with the destination.

The ‘slap’ is meant, I think, to jolt the mind out of its own created traps. Mind creating the problem of duality then trying to use Mind to ‘fix’ it.  as Watts put it “You can’t lift yourself up by your own bootstraps. It won’t work! It won’t happen! “