Ok now that you got a bunch of responses I;'m going to tell you how they REALLY do it in the porn films.
In a shaker put about 20% lube and 80% water... Shake the hell out of it till it turns a bit clowdy white. Use some kind of Turkey Baster thing to insert the fluids in your vagina... Make sure you are laying down so the fluids don't run. Turn on the camera and then using your Vagjj muscles squirt the mixture out, it might look mike a more impressive "gush" if you have a penis penetrating you at the same time.
There you have it.
-BRR