People really just cobble things together, hack them together with stitching really. Depending on what style you're trying to use, you can use the website as a source and try to recreate it. Some people like using photoshop, others might prefer excel. I think Excel is pretty easy to use and (somewhat painstakingly) copy the style of a site.
It's really just practice and willing yourself to mess with it, because it is a hassle.