Cleaning Cleaning willow bark?

[Rosewhite]

So, I guess this isn't bedding per say, but it's in their cage and my Coconut sleeps on it and spends a fair amount of time just sitting on it, so I felt this was the most appropriate category. I bought my guinea pigs a willow hide-a-way. It's a tunnel/arch, and Coconut decided that, to be used properly, it must be turned on its side. This, unfortunately, means that it gets poop on it and in-between the twigs. Is it okay to clean this off with water or is the best I can do is try to wipe it away with a paper towel?