What's in a handshake?!

It is a matter of traditional etiquette to shake the hand of a person soon after an introduction and possibly adding a civil niceity such as “Pleased to meet you.” The origin of this practice apparently stems from the need to prove/see that the person has an empty hand and not one carrying a weapon. I suppose that in the past, the handshake was given a bit less quickly than it is offered today. My question is this. Assuming that the handshake does imply (socially) a benvolence between the parties, is there a way to withdraw that assumption once it is given? I’m thinking of the many situations in which, upon learning who the party is or what he/she does, etc, that one would have refused to shake the hand as an indicator of dislike, displeasure, or antipathy. Does anyone know of an appropriate and meaningful social convention for this? I have seen people act as if they are wiping the hand clean of an imaginary soiling, but this has always seemed a bit weak and juvenile. Would words be a better solution than trying to counteract the ritual with another accepted and understood ritual? I shake a lot of hands that I wish I had not—please help if you can! Thanks to all!

I guess the point of any social convention is that it’s widely understood. If you’ve missed out on hearing of such a thing, you can presume it doesn’t exist. Or even if it did exist, you can presume the other party has never heard of it, and would respond with bafflement to what would look like a weird gesture of malediction from you.