What would you like to know about texturing in Blender? The easiest thing to do is to learn about UV Mapping and cutting. What UV Mapping is is it takes the all of the faces of the model and lays them out flat. You have control over how the faces are laid out by cutting seams in the model.
Think of it like this, you know how cardboard boxes are all created by just folding a single, cut piece of cardboard. That single piece is like the UV map and the final box is like your current mesh.
There are good tutorials online, I recommend finding ones that use Suzanne as an example, because she's a fairly complex mesh (most just use a cube) that will help you get your head around texturing.
Your desk and holder look very good. Is there a reason that you aren't using smooth materials for the pen holder or did you not find them yet?
You mentioned that raytracing is taking a long time. One thing you may want to do is find the Octree Resolution (it's in the Render Settings) and making it 512 as opposed to the default 128. Also, the reflections probably aren't what's slowing it down (unless they are blurry reflections,) it's your shadows. I notice that you are using soft shadows, those take a while.
Nothing is impossible
