Using 'something you know' it's possible to both verify how your vote went and at the same time not allow someone else to know, even if forced. A simple exampl

Using 'something you know' it's possible to both verify how your vote went and at the same time not allow someone else to know, even if forced. A simple example would be assigning a random color to each option per person. So blue means Trump for you. Hilary for someone else. You only need to get people into a booth once, to learn which color is which option. From there on in, verification is as simple as looking at the color to make sure it's correct. No one else can be sure what the color means. Same principle can be done on multiple votes, though information will leak. So if you're coerced more than once you'd need to regenerate your colors. So while this solution stops the 'violence' coercion it won't stop 'sale' coercion. Also the other problem is people will write their colors down or forget them - which is why as you say verification after the fact causes way too many problems.