I have only used keentools facebuilder to make head morphs for Vam. There's a bunch of extra steps involved to get it in a useable state. You are going to need to use R3DS faceform (formally Russian 3d studios wrap) to wrap the gen2 model to the new face shape, I believe it also can do the textures but its somthing I've not dabbled in as I demand the highest quality skins possible on my models and that means Rens skins.
A very high level overview of what you need to do to achieve this is below
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A full step by step guide would take me most of a weekend to write...
This here video guide series is excellent at showing how faceform wrap works for use in Daz. Watch this to understand how things work in faceform wrap and how to get this into daz as a useable morph. You will be doing somthing slightly different as there's only a head bust from facebuilder and the guide covers wrapping a full 3d scan.
Here is the wrap template I use to wrap facebuilder heads.
drive.google.com
You should just need to repin the models, do the wrap then export the model and import to Daz.
Once into daz you need to split the head from the body as this will be a very ugly thing at this point. You need the Shape Splitter scripts to do this
https://www.daz3d.com/shape-splitter
Think of shape splitter as a very advanced morph merge tool, you can use this to select only the head portion. Shape slitter can then line it up with the model and reset the rest to default. Once done you can export the morph and drop it in vams morph folders.
I think what Haz is referring to is
Daz Face transfer 2 and the companion
corrective morphs which is much simpler to use. Its a Daz plugin that can take images and make a gen 9 head from them. Its just a case of using it to produce a head then using Chokaphis
Daz Generations plugin for blender to convert it to genesis 2. You then need to use shape splitter to fit the new head to the g2 model as the genesis 9 model has a very different default head position to G2. Textures get converted using
Mrgigglys texture conversion templets for blender .