Finding electric potential seems easy. Once we understand that we can add the contributions to the change in electric potential energy for our test charge like numbers since voltage is a scalar, it became easier to see. But electric field is much more difficult. How do we add all the contributions to the electric field. We had to spend some time with that one.
We also got into a long discussion about how the electric field from a long plate of charge could end up being constant, no matter how far away you were from the plate. That was a difficult one, and I don't feel my answer was the best. I have a great answer, but it uses calculus. In fact, I have more than one good answer that uses calculus.
We finished the day talking about electrostatics and conductors, which sounds boring until you google things like Faraday cage video or lightning scars on body.