A note on UV maps. You really want to use the Base male or Base female UV Layout. When you select a skin in Vam or Daz3d, some models will use other UV Loayouts like Victoria/Olympia etc. which I think use slightly different texture layouts which slightly warp the textures. `
^^^^ Critical otherwise you characters will have really bad melty look lol... you can use the others, but you have to practice with what VAM has included in the optional skins as a base.
Big tip: If you are using DAZ and exporting the mesh, make sure to make everything the BASE resolution prior to exporting the OBJ, it'll help a lot with the GEN and TORSO alignment. I've attached some templates that will help ...
1001-Torso with GEN - I've create photoshop actions to combine them, makes it easier
1002-Torso
1003-Face
1004-Limbs
(They're png and i made them transparent -- You can flatten them to look like the one on the left)
Create a base OBJ File to work with for G2F : DAZ export (Base resolution body and gen) -> BLENDER-> Create UDIM files / OBJ Export Base G2
FACEGEN -> Get raw face from and image, export to PNG
Photoshop -> Adjustments and touchups, high and low pass editing, details (PIXIMPERFECT)
Substance Painter -> From The blender export with proper UDIMs, create new project and import the OBJ created in blender. paint away
Export the textures, and recombine the torso and gens
Wash, rinse, repeat over and over until you are happy.
Everyone has their own way, and that is like a 50,000 foot view of what i do . Just thought i'd throw in some more confusion for ya. J/k... there are some videos out there on creating G2F or really any Genesis texture. The same concepts apply to all of them. It really just takes a lot of trial and error. I've been doing it for like 15 years, but still find new stuff.