Mapping with wood splinters

[Sam Conifer]

(Working in Gimp)
I want to create a map that looks like it was inked onto an unpolished wood table years ago. So that means that the table needs to have for one oilish stains from heavy use of hands and arms as well as stains from writing utensils, food and drink, and other things. This I think I can accomplish as well as I would like with plasma and channel mixing I think. However what I can't figure out is how I might have missing splinters of wood from say nervous cartography students with sharp objects. Anyone have any ideas?
What I have so far:
http://www.cartographersguild.com/at...9&d=1299183961

Most especially I want to mark up the inner land shadow. Oh and if it could be accomplished without brushing, that would be ideal

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Okay. I think I have found a good way to do this is to:
1. new file
2. fill with color of choice
3. add noise. I used hsv noise with the settings 2, 3, 10, 83 for holdness, hue, saturation, then value.
4. motion blur. 90 degrees, 25 length.
5. duplicate layer, desaturate, 40% opacity, mode = soft light
6. cartoon
7. lwarp to add in knots if you want them. For my project I didn't.

My question now though is if it is possible to have a layer that doesn't add pixels but instead applies a series of filters and/or color changes to the layers below it. I really would like to use these kind of rough wood effects to about 10 different layers, but not to a couple others, and I would like to not have to flatten everything.