Once you get the hang of some basics, scratchboard is not difficult. However, there are some tricks that can make the process more enjoyable. Check out the following tutorials:
Russ McMullin's Scratchboard Tutorial This is a basic overview of scratchboard. It has an explanation of the tools involved, getting a design onto the scratchboard, methods for adding color, etc..
www.dianalee.com Diana's tutorials are great. She explains basic techniques, as well as some great methods for adding color. Her animals are exceptional.
www.inkart.com Michael Halbert, a professional illustrator, takes his individual projects as case studies. He shows each project step-by-step, from start to finish. His tutorials are also full of useful Photoshop tips.