Yes, I do use freezer paper on the back for stability. I find that it keeps the fabric from moving around while you are writing, and I pretty much use it every time. I just rip off a piece, and iron it to the back.
I don't need to heat set it, because I use pigma pens, and they are forever without heat, so be careful, don't write on your white pants while using them! They come in all sorts of colors and thickness.
I get some inspiration from various books on the form of the letters as well as some of the fancy loops. My favorite book is called The Technique of Copperplate Calligraphy by Gordon Turner, ISBN 0-486-25512-3.
If you have some extra lunch money burning a hole in your pocket, perhaps you want to surf on over to Purl and pick up one of their Liberty of London fat quarter packs.
Liberty fabric (to those who are lucky/crazy enough to own some) is what fabric looks and feels like in heaven, I think.