multiple image selection for column portfolio type

I am migrating an existing site with multiple galleries to portfolio post type, Each gallery (and therfore each portfolio item) will have around 70 images. I want these to display as masonry format, so I need to use the “column” portfolio item format. The problem is, this way I need to attach each image one-at-a-time.
Is there a way for me to select MULTIPLE images and attach them to a portfolio item at the same time? Otherwise I am stuck with adding around 500 images one at a time.