Disassemble your valve. I am not going to be modding it as it is really unnecessary for this project. Taking it apart simply makes it easier to paint.
While the paint is drying (if you choose to paint), now is a good time to cut your tubes if you have not done so already. PVC saws (looks like a metal string) are cheap and effective. I personally use a band saw to zip though everything. Guitar strings also work, just be very careful - it will eventually snap and the filament will be extremely hot (I've had burns from this). Guitar strings also have a tendancy to wrap themselves around when they snap.
Now is also a good time to sand off any burrs and lightly sand the mating edges of the fittings and tubes.