The airbrush method or rattle can is the only way to get a brushless look on the translucent areas, especially if you want a factory appearance when the lights are on. On pinside there is a Topic for repainting a backglass on a Sky Jump. Also Johns Jukes has a page on their web site regarding backglass repair.

A large art supply store should have the translucent style paint for glass. Thinking I've seen something like that at Micheals. You may have to mix a color to match the current color. Look on You tube there must be vids on there for 'Reverse Painting Glass'.

If you could find a retired sign painter, or a hobbyist that does fake leaded glass windows, possibly?. The other might be to take it to a old school sign shop that still paints signs. It is possible that they might be able to repair it. It could get expensive, paying by the hour, for someone to scape off the old damaged artwork area and re-spraying it with an acceptable color.