I don't think that would be useful with the free version of Sketchup, as it cannot import obj. Actually, I'm not sure that Sketchup Pro can do it, either, come to think of it.
The major problem with texturing in Sketchup is that it doesn't have any UV tools. Without the ability to unwrap the model, you have to texture each surface individually, and it's difficult to get your seams to look natural. I'm afraid I can't really offer any advice on SU texturing—I've really only used it to pull geometry out of the 3d Warehouse for use in Maya (easier said than done, by the way).