I use a Dremel saw with the blade sit to 1/4" deep. Be careful not to cut too close to the toe rail. The outer skin and inner skin join there. I've attached a photo so you can see what I mean. Here is a link to a dropbox with a bunch of pictures of my deck recore project.
https://www.dropbox.com/sh/88ftelcej...rmwx9RYba?dl=0

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