The traces are not really the problem, but the leads sticking down from the board. I think plastidip would not be resilient enough against vibration against the pins for a long term solution. I actually have a can of conformal coating somewhere that I was going to use for it, but I could not find it anywhere..
The cardboard, while a little ghetto, does work pretty good though!
I am still trying to figure out this dimming problem.. I pulled out the Multifunction switch, and tested what it does with a multimeter and it works as I would expect. I reconnected the MFS to the cluster and now it works fine.. except when I reconnect the car to the MFS.. then it goes all fubar again.
Oh, and yay for accurate tachometers!