Can stacking multiple exposure images in post-processing give the same effect as a long exposure?

I like to shoot daytime long exposures, where the exposure time is around two minutes. That shows the motion of the clouds in daylight.

I used a Hoya nd400 (which is 9 stops) stacked together with a cpl (around 1 or 2 more stops down) but i couldn't get the 2 minute exposure. So i would like to know can I get a final image with the same result as 2 minutes exposure, by taking multiple exposures and stacking them together in photoshop.

For example, I could shoot 6 images which have 20 seconds exposure each (a total of of 2 minutes exposure) and stack them together in Photoshop.

I don't know much about Photoshop — how would I go about doing it? I want to get same effect of that 2 minute exposure photo by stacking multiple exposure shots with stacking or blending layers — but, how?