The only time I washed my ghillie was when I slapped mud all over it to break in the jute, and to "naturalize" the colors. I simply took a hose and washed it down. But since then, its been around 4 months since I hosed down my ghillie.
When it gets wet during a rainy game, it smells like wet dog. Its horrible, especially since I keep it in my room. Sometimes it smells like plants from the veg I leave in my suit. Nice and natural, thats how I look at it.
The only time I would hose it down is if a bunch of bugs and critters decide to set up shop.