Not that I've found.... The way that I do it is kinda embarrassing but I'll lead you through it, I basically taught myself :P
1. Make sure you understand the basics of TSRW or CTU or S3PE 2. find your new texture, you can find some at GoS that people have posted or you can extract one using S3PE or TSRW or CTU whatever
3. Depending on where you got your texture from it probably doesn't cover the entire hair, if you extracted one try to find a hair that has a texture that goes most or all of the way up and down, then copy the big part and paste it so that the texture is continuous, then save that
4. Open the hair that you want to retexture, then paste your new texture
5. This is where it gets a bit different I use GIMP and so I have no clue how Photoshop and other programs work
6. Look at the layers tap you should see the original texture and the texture you just pasted, now click on the filters tab just a little above that (I'm pretty sure it's called filters)
7. There'll be a big drop down of effects, play around and see which one you like best, you can do it multiple times
8. Once the texture looks how you want save as a DDS file in a DXT3 compression with midmaps
9. Put back into the hair file
10. There are already tutorials out there for the speculator and control map
I'm not saying that it's the best way but it's how I do it :/
Grah! Thanks for this! I'm getting stuck when it comes to textures....I'm not sure how to extract them, because I open the package in S3PE and all I get are a bunch of instance numbers. I don't see DDS files anywhere, nor am I sure how to get to them. That hair basics tutorial isn't helping at all....
Ok, I found the DDS files. Now...what's the next step? Do I somehow extract them and put them back into the package after editing them in photoshop? I do know how to EDIT the textures...I'm just not sure how to take them out and get them back in again, or which IMG files I'm supposed to mess with.
In S3PE, right click the _IMG, hit Export... to file, don't change the name, and edit the resulting DDS.
If you want your retexture to replace the original hair, and the original is a custom hair, then rightclick the _IMG again in S3PE and hit Replace, replace it with your edited DDS. Save and voila.
If you want your retexture to replace the original hair, and the original hair is an EA hair, then open S3PE, go File -> New, and import the DDS (or DDSes) without changing the details.
If you don't want to replace the hairs, it gets a bit more complicated - for EA hair you can clone the hair in CTU and then import your DDS in the Textures tab. For custom hair it's more complex, as I don't know exactly what you'd need to reinstance.
What I lack in decorum, I make up for with an absence of tact.