I need some cookie help. I've only done decorated cookies a few times before. They did ok but I know I could make them better.
How do you flood the inside of the cookie with RI?
How do you know how thick to get it?
Is there any way to make it not look so shiny?
Is there any good place to read about how to do cookies or do you know of any good books. I really want to make some but I feel like there is so much I don't know.

There is an article done by antonia74 that really helps. They don't stay shiny. Just give them a day.

http://www.cakecentral.com/article54-How-To-Bake--Decorate-Cookies.html
to thin a small amount of RI, add water drops at a time until a piece of icing dropped into the pool disappears at the count of 10.
RI shouldn't be shiny (Wilton Color flow should be)

when piping, remember to let the icing fall into place and don't draw with it (well sometimes wou do, it just depends on the look...)