I ended up having to do this job.

I have had bad luck with butt connectors, probably because I have cheap crimper and you need to really match the connector to the wire size.

I would recommend this method show in the photo.
Just do this order:
1-Strip all of the wires with ~3/4" exposed.
2-Put a piece of heat shrink tub onto every wire on one side of the job, for this job put a shrink tube on every wire in the cabinet.
3-Bend them into a "J" like in the photo.
4-Match all of the wires with their "mate", twist up and solder like in the photo.
5-Once they are all soldered go back and heat shrink the tubing on.

By doing one operation to all of the wires before you move onto the next operation you can really move quickly. The biggest chunk of time is spent matching the wires up. When I did the job I matched up and did all of the obvious ones that did not have any look alike wires. Then you are hopefully only left with a few that need to be traced out with a DMM.

I think this leaves you with a fairly clean looking splice, cleaner than what a butt splice looks like.

splice.jpg