We do all of our electrical and fire alarm riser diagrams individually. As AFab suggested, we have blocks of the standard items for the riser that we pull from one template drawing over to the new drawing. If you do it once and save out the drawing/blocks out to a spot everyone can find and use, it becomes so much easier. And the price is low - free. It only takes your time to create the items and save them, time that you might have spent researching, buying and learning another overlay product.
Now if you are doing massive amounts of wiring that you need to keep organized it could be a different story, but I know what works for us and our simplier diagrams.