Finish the game as Alucard. Now go to a new game and use the name RICHTER. This will allow you to play as Richter Belmont. Now you just have to make your way through the castle as Richter and defeat Shaft in the Clocktower area of the inverted castle. You do not have to fight all the bosses again, so try to make your way straight to him. Also make sure to make good use of save points as they will refill your health. Best way to kill shaft or any other boss encountered is to use holy water, and don't forget you can chain your super jumps together ( then ) to reach really high areas.