Hi Nick, I'm also new to this site which seems to be a very good one.
I have been making dovetails without a jig having followed a technique explained in a video which came to me free with a subscription to Time Lifes collection of wood working books.
The books are terrific and the video brilliant.
The method shown uses NO measurements and uses an absolute minimum of marking out. The resulting joints are accurate and have that genuine craftsman look about them.
It seems an expensive way to get a free video but there is no other!
If I can help more, please ask. Mike - Surrey