I made the drawings in Autocad, though I expect any CAD package would be comparable. I didn't find it hard to learn at all, but YMMV. While Autocad is way beyond what anyone not in the business would probably buy, ACad Light and other CAD packages are very reasonable. I think there are even some free Cad packages around... Once i had the basic drawing done I exported the line art as a wmf and then opened it with Paint Shop Pro, enlarging it as I went. Then it was just a matter of coloring it. Most of that is flood fill but some painstaking little dots had to be touched up one at a time... Once the art was done I saved them as tiff files and then pasted them into a publisher layout and added the text. Then I pdf'd it with Acrobat, though pdf995 is a good solution for those on a budget.
I finished that whole process in a single afternoon.