I guess I was lucky that the automatic calibration worked first time without any manual intervention. To print the model, I followed the instructions in this post (Step-by-step creating a two-color Snapmaker print: from Fusion 360 to Luban (with the dual extruder)) but instead of Fusion 360, I used Tinkercad.
I believe you should try and use the dual extruder you purchased. Whatever happens, I think it’s a shame to leave it sitting in its box.