Nice work everyone! - Some really interesting textures among these; I look forward to seeing what creations people come up with. That one I did before wasn’t difficult - it took just over an hour to reach that stage. I think the looseness works well with the ethereal nature of the subject.
I’m hesitant to say anything it impossible in Krita due to the number of brush engines and huge array of options. This kind of effect is very complex though due to the way the pigment behaves on the wet surface and just isn’t possible with what we have. Rebelle can emulate it to a degree, but it’s still limited against using real media because of how you can manipulate it physically.
You can emulate the look of watercolour brushes quite well though - I think Pesi’s brushes are pretty effective in that respect, and Ramon has some similar ones such as those in his Atelier bundle.
The closest I’ve come to watercolour behaviour myself would be the experiments I did last year:
There are many ways you can add randomness to brushes - rotation, scatter, size, ratio, animated tips, masked brush combinations etc. Then you can also do clever things with layers - building textures in stacks with different blending modes to create interesting interactions. You can create very organic looking textures, but not quite like these real fluid interactions.