I like to prepare the board by adding a little of solid to the area first.
This is the cross reference keys I get from this particular keyboard, Note not all the keyboards are the same.
I separated the wiring by Sections, all keyboards are a mix of wires per example to get a lower case letter "a" is just one wire from section A and one wire from section B if you at max you will get in between 35 to 40 buttons if you need more you can mix three wires and you will get Upper case etc...
this is what I get from this keyboard, just remember that not all keyboards are the same!
This is the button box I build for the keyboard.
Those are the buttons I purchase from ebay.