Using mirror lockup on 5DMK4 with intervalometer

Recently purchased 5DMK4 and still learning all the features. I've tried quite a few times on the camera itself and have googled multiple sites, but the question I still have is, with this camera can multiple exposures be made in Bulb mode with an external intervalometer and mirror lockup? Say I want to take 6-30 second exposures, if I lock up the mirror to begin the sequence only every other actuation is being recorded. I can enable the mirror once again and then every actuation is recorded.

My immediate hope was to take a long exposure of a rocket launch, though guess it could be used to take night sky images and was concerned with the mirror vibration. Thinking if I took 6-30 second exposures and stacking rather than a single 180 second exposure it might give me better control of the exposure in post. Or am I over thinking this and just take a single long exposure?

Thanks!

Turn off the mirror lockup in the camera and start your sequence with Liveview being active. That way the mirror and mechanical shutter is already open so there is no movement at the start of the exposure. At the end of the exposure, the shutter closes and the image is read out. Then the mirror comes down and back up again to return to liveview. The intervalometer repeats the process.
Your mirror lockup time is now however long you set the delay between exposures.

Steve.