custom post types accross themes in migration


As WPMUDEV tools' usage in the day to day business of managing website projects for clients as well as developing a powerful solution for wallplay increases, we are curious if WPMUDEV has a handle on a common snag.

Custom Post types from themes such as a portfolio or project post type is often generated by the a theme itslef. If we are wanting to maintain the content of a custom post type from an OLD theme as a custom post type in a NEW theme that may either have a plug in to map them to or a created post type with the custom post type plugin... how would we best go about the conversion?

Any thoughts?

Client A has a site with 300 projects (a post type specific to the old theme being phased out) We migrate the site to a solid host like WPEngine, Network Activate the Multisite function, clone site and make a duplucate to re-skin with new theme. This new theme does not have a custom post type.

How precisely can we avoid manually re-entering all of that content?

This problem has probably been solved many times in the past.

Any advice?

Thank you in advance WPMUDEV Rockstars