How to expose Canon 600d for many times?

It is theoretically feasible to use B-gate multiple exposures in 600D, not to mention the dark light and small aperture. First, fix the camera on the tripod, adjust various parameters, and then press the B door. Method 1: flash the subject once with a flash, and flash the subject twice ... n times by changing the position (angle). Method 2: The blackboard blocks the lens, similar to a flash. The difference between the two is that the flash mode requires the scene light to be close to all black, the lens mode is blocked, and the scene light should have a certain brightness.