Another problem you may have is ground is generally not carried to the switches. Most controllers, be it WiFi, BT, IR, or whatever will require both 12V and ground. They might require 3.3V or 5V.
However, both 12V and ground can usually be found at the light fixture when the switch is on. You might be able to find small low side controllers and tuck them behind the light fixture on the ceiling.
If you have a switch that controls numerous lights, locate the controller at the 1st light fixture to control them all.