OK so I have read and re-read and read again the Blender reference manual. I have watched dozens of video tutorials, and have read countless others. But I need a to find out what the relationships are between materials, material slots, textures, texture slots, paint slots, texture painting, etc. etc. etc. I do NOT really need to watch another tutorial showing me what CAN be done in Blender. I already know how good Blender is. What I need is something to explain how these things work together. The reference manual isn’t really detailed enough. And many of the tutorials either go really fast, and pausing and rewinding make it hard to follow along. But most of the time, the “teacher” will tweak something or correct some little things (check or uncheck a box, etc.) and they don’t mention what they just did, so I can’t follow along because they’ve left out one TINY step that makes all the difference if something works or not. So, if anyone has a suggestion for a tutorial that explains the basics and WHY and HOW these things work, and work together, I would love to see it. I have tried lots of settings and so forth, so it’s not that I’m lazy or not trying. I thought I had figured out that I need a material slot to hold a texture, even if there is no “material”, but then I see tutorials where a paint slot is added in texture paint mode, and it works, But it won’t work when I try it. I am OK with nodes, but no expert. But trying the nodes approach didn’t do what I expected. It’s just all confusing, and I know the answers are out there somewhere. Any help in finding a good explanation will be appreciated.
If you have already watched and read dozens of tutorials it would be helpful if you give some more insight into what you understand, what you think you understand and what you know you don’t have a grasp on. Simply watching another tutorial seems like a low-effect solution at this point.
Do you know how to setup a basic diffuse shader with a texture that uses UV coords?
Do you know how to set up a simple plastic-like shader?
Do you know how to use bump/normal maps?
Do you know how to use procedural textures?
Etc…
If not, what does not work? Show your nodes and describe your reasoning behind your setup.
The following 2 tutorials were real eye openers to me. They are both written instead of a video.
Thanks for the links. But I still need some basic tings explained. For example, do I need, or NOT need, a material slot in my scene to paint a texture onto a mesh? Some sources indicate that I do, while others don’t seem to do it that way. What’s the difference between applying an image texture to a UV unwrapped mesh, and painting a texture onto a mesh? For me, the result looks different in texture/texture paint mode, but when rendered, the texture painting has not made a difference. It’s basic things like this that I can’t find explained. Most of these tutorials start off at a higher level. But some of us are totally new to this part of Blender. I can setup materials, use nodes (not as well as some people), set up mix shaders, glossy, etc. etc. I can use bump maps, displace modifiers, UV maps and such. I can use weight painting to control particles (hair where I want it), and such. But this texture painting is a mystery. Do I NEED a paint slot in texture paint mode, or a texture that has been opened in the UV image editor? Or just a material with a texture SLOT, or an actual texture??? I think I’ve reached my limit with Blender, and I’ll just do what I can. But I know my stuff doesn’t look so good.
It takes time, ive been doing 3d for over 2 years now… and im still learning new things pretty much every day. Just keep at it, and don’t give up! nothing worth learning is ever easy 
You need a texture slot and a blank image. And the mesh must be unwrapped.
Best to use a generated image, Which you can create in the U.V editor, just choose create new image, set the resolution you want and name it something i.e Diffuse or Grunge etc 
You can then paint directly on to the model in texture paint mode once you add your generated image into a texture slot, or you can paint onto the image itself in the U.V editor (Just set the the button “view” to “paint” at the bottom of the U.V editor window)
edit - This explains it further, as i think things have changed a little since i last used tex paint - https://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.72/Painting
The problem is that saving the Blender file does not automatically save any image you’ve been painting on in the Image Editor. Make sure to Save as Image once you’ve done some painting, and then assign that image in the Texture panel as an Image texture, otherwise all your good work will be lost. So you can create a Texture slot in the Paint window, but it’s not permanent.
Christina, thanks. OK I understand that I have to save the image, but even if I’m still working on texture painting something, and switch to rendered 3D view to see how it looks, there’s nothing there, just white, etc. Also, sometimes the texture paint tool panel shows an error that there is no texture slot, but the only option I see in that tool panel is to add a PAINT slot, not a TEXTURE slot. So how do you add a texture slot if you get that error?
Hope this helps