I 'band' before (since I often pre-poo and detangle before, and like to keep it sectioned and stretched while washing) and band after shampooing. The before banding is loose so I can get to my scalp when I shampoo, but it means the hairbands I use (ouchless) get wet in the shower too so hopefully don't dry my hair out. This is when I'm wearing a stretched fro.

If I'm styling in twists, I won't band properly after shampooing, just keep the semi-stretched sections and I'll twist my hair up while it's still quite damp.

If I'm wearing a wash and go, I'll take the pre-wash bands out while conditioning and leave them out.

I band because my hair is too thick to stay in twists at this length. I know twists keep tangles away better and dry quicker, so sometimes I will twist and then band the twist with one band just to keep the twist in. Otherwise I'd have to do about 12 twists to make them small enough to stay in, which is too much effort just to stretch.
/essay
My hair is in the 4s, low in porosity, high in density and coarse.

Love: QB - all of it, Bobeam - shampoo bars, Darcy's Botanicals - Pumpkin Seed Conditioner, Coconut Cupuacu Pomade, KBN - Shealoe Leave-in, Oyin - Juices & Berries, Kinky Curly - Knot Today, Ayurvedic treatments, my Denman and the cloud of kinky goodness on my head that I get to play with!