great stuff on multiple walls

I did the back and ran out of GS. I now need to do the sides. The back has already set up a bit since I started at 9pm after Lowes and Home Depot closed.

When I flip the tank to do the sides tomorrow should I do any prep to the back that has already cured? Sand the edges where it will join the wall or something like that?

I know... measure twice cut once applies to buying supplies too. :(