The simple solution to perfecto scarfs...

One of the things about tools is that they can vastly improve your workmanship and in some cases really save a lot of time. I can't think of a better example than the West System Scarfer which fits on your circular saw only does one thing but it sure does it well.

Of course, you can set up a jig for your router or electric plane and some of us have been known to simply just do it by eye, but for plywood 10mm and under the scarfer simply kicks some serious butt...