A lot of people turn the analog button off and noise to zero in Waves plugins, but in doing so they’re missing out on some of the magic.
The analog buttons often enable harmonic distortion, and it can range to being a subtle amount to being a rather extreme amount depending on the plugin. Run a 100hz sine wave through the plugin and look at it in a good spectrum analyzer. You’ll notice odd and even harmonics added, and it varies quite a bit depending on the plugin.
As far as the actual noise goes — a lot of people turn it off because if you have a lot of plugins with noise it can add up to be too much.
In that case, use a GATE with a long release. This will give you the benefit of noise without too much buildup.
You could use Waves C1 GATE for this, but I personally prefer the gate in Scheps Omni Channel just because it’s so easy to set and it’s nice to have instant access to all the other tools.
The key though is to allow the noise in without it taking over your song. This also allows you to turn the noise up higher than you might, otherwise, since it’s only present when the instrument is playing and it fades to silence after.
PS. Make sure you’re hitting your analog emulated plugins at the correct level. An average of -18dB (or -12dB peaks) is usually a good level to start with. (Some Waves plugins have a hidden feature that lets you tune the level – typically hidden behind a screw – but it’s better to get used to -18dB average because it’s a standard between most plugin developers.)