Thanks, Pat. I usually do a quick outline with the icing I'm using for the flooding, because that keeps the edges smooth, and then quickly fill it in. Smaller shapes or simple shapes, I'll just go from one side the other when I fill them in. I just did a big order of star shapes, and for those, I worked in concentric circles from the outside inwards. Some shapes that are complex will start to crust a bit on the quickie outline if I don't work from the outside in. In other words, keeping the outside of the shape wet so that there are no ridges when the flooding is complete. Did that make sense?
As long as your icing isn't so thin that it overflows your edges (or contrasting border, if you do that), it's all good. If you flood in your cookie - particularly this happens with small areas - and it looks perfect but you check it a couple hours later and it's made a big hole or has sunk down into a valley, your icing is too thin.
You're right about saving a lot of time by doing it this way. I know a lot of people swear by outlining, and this is one of those instances where all roads lead to Rome: If outlining works for ya and you like doing it that way, nothing says you can't. But I do decorated cookies for customers and can't take a lot of time on something I can do as well without it. Just my two cents there.