Annette - the best way I've found to create transmaps is with a vector point-to-point line tool. That way the points are editable and I can make sure seams match-up, among other things. I always 'draw out' my transmap on a copy of the template and load that as a texture.

Both Photoshop and Paintshop Pro have vector tools (as, I'm sure, do other graphic editors) and it was (literally) an epiphany for me when I started using vector lines to do my transmaps.

I've a basic tutorial for PSP on my site. It's the first in a series of three on this topic. The first tutorial is long, but it really does ground you in the basics. The next two are/will be more tips-and-tricks oriented. You can find it here, at the bottom of the page: Wax Textures

In any case - good luck!
Regards,
-Nancy.