When Sith Lords can't duel each other, how do they practice swordsmanship?
This question is mostly related to lightsaber dueling.
When do Sith Lords practice dueling?
During the clone wars, Sidious and Dooku didn't have a lot of time on their hands to practice against each other. Dooku actively fought Jedi masters so he surely wasn't rusty.
But when and how did Sidious practice? What if he out of practice when he faced the Jedi masters? If that is true, imagine how great he would be if he was on the top of his game. :)