The answer to the question about a kohen hand being touched after washing for birkat kohanim. You mentioned it only if the hand was wet. Does it matter if its dry and someone else touched it?
If the hand is already dry, there is no concern over somebody else touching it. Only a wet hand can be “mekabel tumah” from other hands. The same principle applies for netilas yadayim before food: one must be wary of somebody who hasn’t washed touching one’s hand while they are still wet.