how to clean plaster wall

I have had some termite infestations in my house and the exterminator has finally agreed to do a whole house treatment with Termidor. A second exterminator told me I am getting my money's worth and this should take care of the problem. My house is on a slab.
My question has to do with repairing my wall. The termites did some tunneling about two feet up the wall from the baseboards. The trail they left behind is dirt, I'm told. My wall is dryboard with the swirly plaster design on it and the dirt has embedded into the grooves pretty well. I have used a stiff brush to clean it, but the trail still remains.
Should I use a primer to cover it before painting, or will paint suffice? Is there a way to clean it without painting?
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kilz paint at wal-mart comes in color too

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