The benefit of leaving the slush to freeze is that it adds base to your ice and it's really really heavy (pain in the butt to shovel). I tend to judge my opinion on how my rink is doing. If it's early in the season and my ice isn't quite ready, I'll leave the slush to freeze. If it's in the middle of January or February, I will remove the slush to get back down to my ice since I've worked too hard to get it to that point to start all over again.
I think you did the right thing by getting it to the 1st picture. Hopefully it has been cold enough to solidify your base before the next storm. If not, you might have to repeat the whole process again. Isn't owning a backyard rink fun?
As for the hot water floods, I never use hot water so I'll leave that to another person to answer.
-Kevin
P.S. That second picture looks like a stipple ceiling.