If you are spraying in temps of 72 deg F or above and humidity isn't super bad where it is curing, you can string in 24 hours with no worries.
I have never ever had an issue stringing it that soon and have even done it sooner than that since my shop is ideal MC and used to heat my spray room.
When in doubt, wait 48 hours...hard to even scratch it after that!
BigJim