I wish it was the latter I use the default fuzzy brush with scatter and wet edges applied at a low-ish opacity

and then it’s just lots of layering and varying the amount of spacing/size to make it look more in/out of focus in places, I have come to refer to this as the ‘splutch brush’ in my head :D

I usually do a harder contour sketch first so I know what my key values are going to be, but through trial and error I’ve found that just going pellmell at mixing up the colours like I would with chalk pastels results in the best effect so it all ends up being on the same layer in the end