I waited 24 hours after the second coat of putty before sanding around the patches. I used a 250 grit sand paper for the job. You want to sand all the edges down, when running over the patch with your hand it should feel as if there was no patching done there in the first place, it all should be even. When sanding “powdered rain” will be falling down.
This is the putty that you’re sanding off the wall, so the ground is going to get messy.
Before and After.. rather After and Before