Darth Plagueis was alive up until Palpatine was named Chancellor. Darth Maul was a match for Jedi Masters. Darth Tyranus was a very accomplished duelist even before becoming a sith. So I would say it was through training/sparring with his master and apprentices as well as the use things like training droids.
How did palpatine keep his skills sharp throughout all those years without attracting any notice?
Darth Plagueis was alive up until Palpatine was named Chancellor. Darth Maul was a match for Jedi Masters. Darth Tyranus was a very accomplished duelist even before becoming a sith. So I would say it was through training/sparring with his master and apprentices as well as the use things like training droids.
How could that be true? He already had an apprentice before he became chancellor, and there can only be two sith at a time