I have restored backlit pointers quite successfully by removing them (duh), then using 400 grit wet/dry sandpaper, removing ALL the old [now yellow] paint from the back so you-- as Richard Nixon used to say, "...make one thing perfectly clear". Then use a fluorescent orange spray paint on the BACK of the pointer that you so nicely cleaned off.
Best way to put the pointers back on properly (calibrated) is to hook the stuff back up, turn the ignition "on". All guages should point to the "home" position then. O MPH, 0 RPM, etc.