Sorry no tutorials are available, but you’d have to order an xwhatsit, solenoid driver, and solenoid. The XT PCB is connected to the controller. I would not recommend this as you risk breaking a PCB that they don’t make anymore, but others have succeeded doing this to save a broken XT.
I recommend putting the funds instead towards the new Model F keyboards for those who have not done so already, as they have plug-in solenoid support, no soldering needed and you don’t need to spend $50 on the controller as it would be included and preprogrammed. I can even install the solenoid and solenoid driver for you in your new F62/F77 (the installation fee was mentioned in one of the other Q&A posts).
Once you cut off the old XT controller, you can see there are 12 column pins and 8 row pins (zoom into the below photo), while the xwhatsit controller offers up to 16 column pins and 8 row pins. The manual on this project web site will show you the order of the pins to solder from the controller to the xwhatsit. Please note the photo below shows an alternative prototype controller from a few years back (someone else’s project not xwhatsit). Then you can use xwhatsit’s firmware, via, or the QMK firmware. For a unique matrix layout like this, xwhatsit’s old firmware (with the latest updates – version 0.9.3 available in the manual on this site) is the easiest option.
https://i.imgur.com/SnTT8uc.jpg