Merging textures together

[Lancelot]

I'm currently working on a small texture project, just for myself. One problem the models have is the fact that most heads not just have one texture, but two separate (one for the face, the other for the head). Because of that, it's difficult to modify both textures and make the result look seamless, if you know that I mean.

So, my question is: Is it possible to merge both textures together and make only one texture out of it? It would make working on the heads a lot easier.

[Circa]

Merging them into one for the model to use would require remapping the UV maps, which would be a lot of work. 
 

What I have always done is just copy and paste one into a new layer on the other and work on them both in one project side by side there, and then flatten it down, copy and paste it back to the original and save both.

[NumberWan]

Substance Painter might help with this, but it can be tricky as well. I still prefer PS for most of texturing.

[AshuraDX]

Could also use the 3d features in Photoshop