How to soothe sunburn and help the redness go down overnite?

No fast fix. There's no fast fix for sunburn. The following may help: keep it cool with ice compresses/cool towels. Keep it moist: aloe vera gel or moisturizer. Decrease inflammation by taking over counter anti-inflammatory medications such as Ibuprofen or Aspirin per label instructions: (aspirin not recommended for children or teens as may cause reye's syndrome).