As for the tutorial, the process has been gone through many times in thread, even recently, just look back some pages.
Worth noting that merging is somewhat trivial, upgrading these techs from one engine version to another always isn’t. You need to track down engine API changes, do cross referencing between other engine components to find how you should use certain things on the new version etc, it’s a bit of a detective work and not all that straight forward process that someone could write 1,2,3 step guide for. For example it took me multiple days to get FleX fixed where Volumetric Lighting didn’t require any changes on the engine side from 4.19 to 4.20. But I do guarantee that VXGI2 and Hairworks both require a lot of manual work, it’s the main reason I didn’t port them.