I often get questions regarding various topics on scratchboard from tools to transfer papers- so below are the answers to some of those common questions.
Best place to learn about scratchboard and get feedback on your scratchboard work - Wetcanvas! Scratchboard Art Forum - wetcanvas is a free online art community with forums that cover all topics and all mediums. There is a very active scratchboard forum with some outstanding scratchboard artists that are very helpful and full of good advice. The members are from all over the globe too!
My favorite brand of scratchboard - as far as I am concerned there is ONLY one brand of scratchboard and it is made by ampersand. It can be found online through various artist web sites including ASW Express (good prices and inexpensive shipping in the US). Unfortunately it is only available in the US, but I know many artists that spend the $$ to get it shipped to them overseas.
What tools I use - scalpel blades #11, exacto blade #11, speedball scratchboard tip #112 and 113, very small fiberglass brushes, fine grit sandpaper, oil free steel wool
My favorite transfer paper - Super Chacopaper (many sources online and can also be purchased at Michaels craft stores)
Where to get free photos that can be used by artists as references? - I primarily work from my own photos, but if you are not a photogapher and/or can't find what you are looking for check out Stock Exchange, Morgue File, Wetcanvas! Reference Library (must be a member of wetcanvas to access), Flickr Creative Commons (scroll down to the bottom and click all of the boxes by creative commons images to be used commercially and adapted). I always recommend sending a photographer a note asking permission before using a photo, even if the site gives permission. It is always better to have permission in writing if you are going to use an image for your art that you plan to sell than face problems later on.