Oooh! I really love these kinds of threads~
(I really go on for a while sorry)
Ahh it was exciting when I first discovered auto action. Currently I use it to add effects to my lineart quickly. I make like 3 different copy of the line art and change two of them to overlay and the other to multiply that gaussian blur one of those and lessen the opacity for all of them and change the colors . . . It's a whole thing so its nice to have it automated.
One thing that helped was figuring out how to take advantage more of CSP fill tools, cause even if you don't have really clean line work it still does the job. I also combine it with magic wand since nothing is worse than accidentally filling the whole canvas and CSP lags for like 5 mintues lol. There's also some really good fill tools as shared assets.
Another thing with CSP assets, I sort of just regularly gather brushes and assets I'd think would be useful, they've saved me on more than one occasion. I've also started gathering all my references onto one file and opening that with subview, before I'd just open them individually and it'd be a mess, now its all there. I've also gathered a bunch of textures and images that I thought would be useful from online and put them as materials, so now I don't need to go looking for one everytime I need an "old paper texture" or something like that. It's already downloaded on CSP and ready to adjust.
Finally last thing on CSP, this is more for illustrations rather than comics, but I've messed around a bit with autocolor/colorize and gradient maps. It's a good way of just getting some base color and values to work with. Actually, all the color correcting tools have been fun to play with since I prefer to go for the more "cinematic" and moody look with my comics.
For working on backgrounds, I've started just collecting them on a separate file or making them as their own materials. I prefer to make all my own background/establishing shot materials and I'm rather picky lol. So having my own premade and ready for modifications on its own file has been helpful (like how many times do I have to paint trees or clouds). Now I still gaussian blur a lot of my backgrounds, but its not quite as obvious that they're low effort.
As for my setup, changing to a tablet that has touch was so nice. Been able to just pan and zoom freely saves me probably a lot of time given how often I use it. I really recommend that if you can save more money to get a tablet with touch (really wacom . . . you sell your premium super expensive products with touch as an add-on . . .) its worth it. It also freed up my hotkeys, I have this fancy looking shortcut key remote made more for video editors but I liked it cause it has two dials and 15 buttons. It's more expensive than the cheaper one made by XP-Pen, which I also had back in the day but it broke after like 2 months grrrr. Initially, I thought 15 buttons is a bit overkill and I have a keyboard . . . but nope haha I found a convenient use for all of them and my muscle memory picked them up relatively quickly.
As for the writing aspect, probably where I'm most inefficient, but I've been figuring out how I can combine the writing and storyboard stage without getting losing quality or getting to myopic an losing track of the whole chapter/story. One of the things I've just started doing is I no longer write things panel by panel going down this super long file. Instead I first compartmentalize the super long image into the different scenes, what these scenes are intended to do to the reader (ex, "cliffhanger"), and figure out an estimated length for the scene based on its importance relative to the other events in the chapter. It's been helpful with pacing and using panels more efficiently.
For drawing/art, I also just started going from rough sketch to lineart. I tried to do rough sketch then construction lines then sketch then lineart, but I never liked the product and it felt frustrating. Just doing the first three steps in one drawing and then final lineart has been a lot nicer and I think the product better communicates the feeling of what I originally visualized. It uses up a lot of brain energy, but I think visualizing is probably the way to go (Kim Jung Gi said so! lol).
Also, with coloring and rendering, I'm trying to do "more with less" in some sense. Like rather than focusing on little things, I'm trying to just utilize bigger shapes for light and shadow and being more graphic when I can. Who cares about dumb little highlights on the hair? Especially on an overcast day with a gloomy mood! Its good to know what is and isn't necessary for the story. Also, if I can be a bit more abstract and emotional then I do that as well. It's less about rendering things till they look pretty and more about just capturing an emotion with simpler solutions.
For lettering, which I suck at lol and will always pass on to someone else if I can, I found that typing everything out first, then just copy&pasting it goes by quicker. I also don't make new SFX each time if I can and just save it as a material. With lewd comics it's alot of those "Ah!~" "Mmm~" "Gasp" sort of stuff that repeats a lot.
Ahh this got a bit long lol, just rambling away~ But really, people think these 40 panel per chapter webtoons are nuts, but honestly with an efficient workflow and experience (and an assistant or two lol) it's not that bad.