Yeah what I do is I write the script completely--fully--entirely, and then do about 5-6 drafts before I ever consider drawing. I change my plot a lot as I write. I do research and plan like anyone else but when I write I still change so much as I go because it's really easy to change a script and type more--it's really hard to change stuff later after I start to draw.
After my script feels good, I take some time to do some style studies--figuring out the style that's best for the update schedule and vibe of the story--so I'll do a bunch of practice pages finding the best brushes that I'll use, the best coloring method that I'll use, and size and type of font and stuff like that. Graphic design stuff.
Then I do some character design work, and some world building for backgrounds (which depends on the comic--because for some there's a lot of talking bits and you don't need that many backgrounds, actually--you barely see em because there's only one per episode, really)
And something I'm doing for my current comic is just really trying to get my pipeline solid and fast, so I've been making just a whole bunch of complicated photoshop actions so that my coloring can go quicker but still look really nice. It's been kind of wonderful, and I wish I had done it with earlier comics because it helps me focus on the things I love to do (which is paint and draw and focusing on design and art stuff) instead of things I hate (which is organizing clipping layers and double checking to make sure all my colors are consistent) It looks like this:
I'm working on getting a year's buffer before I'm done, so it'll be a while before I post it, but it'll give me plenty of time to finesse my style, get character designs consistent, and get my actions just right before I go live with it.