Reverb can be used to add sustain

This is similar to how Reverb can be used to create size, but instead use an unnatural-sounding reverb, like a plate, spring, etc. Reverbs for sustain and reverbs for tone tend to work best for single sources and are best used during the production or balancing process. They also benefit from narrow stereo width to gel more with the dry track. Start off with a pre-delay of 25 ms.^[ Mixing Secrets for the Small Studio pg. 295] Avoid setting it so low that it starts to introduce comb-filtering.^[ Chapter 16: Mixing With Reverb]

I like to use them within their instrument group rather than within the FX group. This allows me to create Subprojects without effecting routing.