I'm decently good at panel composition and making things up as I go so I don't really bother with doing thumbnails first (also I write the dialogue on the spot and usually end up adding more gags as I go so sticking to a strict thumbnail is way too hard), so usually I will make a rough sketch of where I want things to go and jump straight to lineart. Most pages in my comic are limited colour so I usually just have to ink the sketch afterwards.
The rare fully-painted page starts out as a rough sketch as well, and then straight to the painting/rendering (no need for inks).
As a general rule of thumb, I sketch out things I have a hard time freehanding (like hands and limbs). Things like props, accessories and backgrounds, I scribble some general shapes to remember where they go but I don't bother really sketching them out.
I'd say panel composition and freehanding things are some of my decent skills so fortunately I don't have to spend too much time polishing sketches lol
(I only have a JPG of the sketch so sorry for how pixellated it is askakf)
The bunnies in that second page are still there but the speech bubbles covered them up </3