Depends on the capabilities of your hardware. It is really hard to do smooth dimming with wireless technologies because it is really easy to overwhelm the transceivers. On a good day, you will get one or two commands to the light per second. Sometimes better, usually worse. This is true for Zigbee, Zwave, RF433, and Wifi devices.
To do this right you will want to use something like Design Pattern: Cascading Timers to gradually dim the light.