http://scorevoting.net/BayRegsFig.html http://scorevoting.net/AppCW
And today Fargo votes on it.
If you say "Each candidate can be given up to 5 points, or as few as 0 points. There are no limits to the number of points you can give out in total (there are X candidates, so you could give a max of [X*5] points)." you're being pretty succinct and direct in the explanation. You might need more poll workers the first few years (which will create all kinds of problems because areas attempting to minimize voter turn out can exploit that) but once it becomes common you hope that people are used to it and know how the system works
The biggest thing is we need to eliminate the need to hold your nose and vote for the lesser of 2 evils. Obviously all republics involve some level of "this candidate is close enough to be my proxy" decision making, but I'm currently stuck voting for someone who was indicted while in office for political crimes because the alternative is worse.
Moving to either system helps break the 2 party system open...which is why nobody in establishment politics is making a big push to get it implemented.
Or is the concern the possibility of confusion around "rank 1-5" vs "Score candidates out of 5" etc
Usability of a ballot system is a big factor when it comes to voter engagement and turnout, so at this point, I would be very happy with approval-method ballots.