My Simplify3D 4.1.2 profile, working with dual extruders on a Railcore running a Duet 2 WiFi.
The scripts use RRF 3.3 features. They also use some of my macros, which I put in the second link. In the Starting Script, you'll want to change var ExtruderCount = 1 to var ExtruderCount = 2 to use both extruders. I recommend in many cases using a Prime Pillar, at least up to the the height where the last tool change happens. The tool change script uses the Prime Pillar to catch ooze during the change.
Let me know if you discover any bugs or improvements.
https://drive.google.com/file/d/1zjCaRsQ1Sq_tyM9pP4bVxSf_cPhMOBzO/view?usp=sharing