Here are a few more thoughts to go with the video on my previous post. I didn’t let the mud dry long at all. As I showed in the video, I used pretty heavy mud, I only added the slightest bit of water to it. The mud was heavy enough to hold it’s shape right away.
If the mud I’m using is very wet, I do let it set up for somewhere around 10 minutes, it will depend on the temperature, humidity, etc..as to how long to wait. If it’s knocked-down when very wet, it will make more of a smeared look. When it starts to set up a little before you knock-down knife it makes much more obvious ridges and sharper edges between the drywall below, and the texture on top.
When I am doing texture like this, I then apply a primer to the wall after the texture. Again it depends on the temperature and humidity, but I have primed and painted in the same day, once the texture is good and dry. I would give a texture like this, at least a day to dry, 2 days would probably be better.