Tripwire thread on various recovered mini-tutorials:
https://forums.tripwireinteractive.com/forum/killing-floor/killing-floor-modifications/3d-and-animation-aa/55519-texturing-tutorial-thread
(also includes Millenia's video texture playlist at bottom of post)
"Enin" site for mini-tutorials (most is dead but here is the working archives):
Metal & Spring: https://web.archive.org/web/20080216055541/http://st.burst.cc:80/tut_enin1.htm
Wood Stock: https://web.archive.org/web/20080215110220/http://st.burst.cc:80/tut_enin3.htm
Basic metal: https://web.archive.org/web/20071221022901/http://st.burst.cc:80/tut_wanna.htm
Plastic https://web.archive.org/web/20080216055552/http://st.burst.cc:80/tut_exess2.htm
Metals: https://web.archive.org/web/20071221022821/http://st.burst.cc:80/tut_exess1.htm
Photoshop Brush set: https://web.archive.org/web/20040607040331/http://st.gaming-interactive.com:80/brushes/photoshopbrushes1.rar
Tutorial Shack Gun Texturing PDF site dump backup:
https://web.archive.org/web/20050909192652/http://st.burst.cc:80/Tutshack.pdf
Fox-Mike Gun Texturing PDF site dump backup:
https://web.archive.org/web/20040407000001/http://st.gaming-interactive.com:80/MikesSkinningTuts.pdf
Stylized Texture painting of a character step-by-step. Uses "Overlay" method of painting light style (Archive Link)
https://web.archive.org/web/20110210182754/http://michaeldashow.com/tips_texturepainting.html
Face texture painting method video by Ben Mathis:
https://www.youtube.com/watch?v=1QKXpaRiTYs
Character painting method by Ben Mathis (iirc this was originally from 2004ish):
Part1: https://www.youtube.com/watch?v=IvLzk8JrEFs
Part2: https://www.youtube.com/watch?v=lwshiFsq9ec
Rust & Metal painting workflow:
https://www.3dtotal.com/tutorial/658-texturing-metal-part-1-making-the-general-surface-photoshop-by-johny-texture-rust-screw
Painting a tank with welds & mud tutorial:
http://forgottenhope.warumdarum.de/tutorials/skinningdingo.php
Photo-texture/painting hybrid method; this style was used a lot in HL2beta (skip to page 66):
https://orig09.deviantart.net/5ef4/f/2007/122/0/4/3d_tutorial___lowpoly_characte_by_athey.pdf
Texturing a Glock VIDEO series (2007 complete tutorial)
http://www.moddb.com/tutorials/creating-a-weapon-for-source-part-2
I highly recommend this one since it is probably the most complete on the "old style" methods. New(er) Methods:
A newer method of painting is done in a hybrid method of painting on the texture as well as within the active 3d viewport, also known as "Viewport Canvas" or some other variation:
Viewport canvas painting method of a stylized gun:
https://www.youtube.com/watch?v=vMg9S5j5bHY
Viewport canvas painting method of a stylized character:
Part1: https://www.youtube.com/watch?v=6VNMLauOUpU
Part2: https://www.youtube.com/watch?v=LLNw4onM_YE
Part3: https://www.youtube.com/watch?v=kM82kaPHAK4
Viewport canvas painting method of a monster character:
https://www.youtube.com/watch?v=2Yr-Pgw3pMw
DOTA2 "Light Bake" texture method:
https://support.steampowered.com/kb/8700-SJKN-4322/dota-2-character-texture-guide
You can use modern highpoly to lowpoly workflow methods to bake out a "Complete Map" which is a render to texture of your model so all the light and bump/specular/gloss/normalmap is "baked in" to the diffuse. To do this you set up all your materials, create an array of scene lights above your model then use "Render-To-Texture" to bake out the complete map or do it in separate passes for more control.
I have made a quick and dirty guide about doing fine tuning and control with baked maps:
My "SkelePuncher" model was a highpoly-to lowpoly render bake using these methods
( https://forums.svencoop.com/showthread.php/44599-SC-5-x-Skelepuncher?p=526924 ) An important thing to note when making Cartoony ,Stylized or Anime models is that you may want to consider using either the reduced shadows flag (QC code $flags 256 ) or even use the Sven-only special texture mode $flatshade which discards shadows and lights the whole texture uniformly. This is best for Anime or painted shadows textures that would normally suffer under vertex shadows. An example of lighting differences here:
http://www.the303.org/tutorials/gold_remap.htm
Lastly my MDL export guide is almost complete (still no full playermodels but working on it)
http://www.the303.org/tutorials/gold_mdl.htm
<3