Like I showed in the links, I get a reference, try to make an outline that mostly matches up to the reference so it has the correct shape to it or sometimes I make an anime 3d model (cuz I used to make 3d models for stuff) and pose it to match the reference. There's multiple free 3d model things you can go to for this like vroid. Then you make a new layer and shade the outline or 3d model (whichever you felt like setting up the base image). You can either just eyeball a a darker more saturated color for the shading or color pick the current color used and make a multiply layer using the same color and it kinda automatically makes the shading color for you but I tweak whatever that value is anyway. You just use that color to shade the majority of the shadows and where the edges of the skin shading is like the booty or some of the back in the links above, I use a large soft brush so it doesn't have a hard shadow. The layer looks like this
You just hard shade the hair and then soft brush some spots later like for some shadows or the transition between the hair color and hair shading. I feel like it's honestly a good enough job if you just find an appealing reference and copy it or make a 3d model to copy it and then do the shading a couple times till you're satisfied. As you can see in the 2nd link, it's mostly just me redoing the shading a couple of times till I like it. I already trained and studied to draw art in the way that ai looks like, so I might be biased but I think ai art looks nice cuz.. that's the style I've been drawing for years among other stuff like 3d models. You can even see in the reva blowjob gif on this page that I didn't end up going with highly detailed skin or hair (like I did in the 2 links above) because animating the frames to mesh well between frames was a nightmare, so I even redrew all the keyframes of that animation to be cell shaded since the dynamic movement made it a requirement.
In this example below, I make a 3d mockup of reva, get a reference pose I made the 3d model match, get some reference outfits of how I might want reva's body suit to be like. You can even see I made the 3d model match the cross stitch body suit reference and then changed my mind to make the 2d flat pixel art version use more of the V shape body suit reference. Then I had some of the mockup sketches of the 2d saved since I was experimenting of a fusion between the V shape body suit and a more classic bunny suit so I ended up sketching that one to see if it'd look correct since it was a fusion design I didn't have a reference for really to just get a pic of.
https://gyazo.com/ccb394b862c9127a5c252de1447c4e54
https://gyazo.com/d2be0b01fd3141c4b99c16e5a0839ef6
Basically, I draw the pics. I have 4 links that show the process of 2 of the drawings I did. One using a general outline folllowing the reference image and then shading in the details and the other one making a 3d model mockup to match a pose reference because I wasn't sure what pose I wanted the characters to be in so 3d models were easy to make a lot of pose mockups to see if I liked it or not before committing. The point is, I showed the resources I used, the process of which I used them and how I made them, my technical knowledge of how to make digital art for how I get the shading, layers, how to do the soft shadows and where to place them and even how making really detailed ai art animations is really hard to make look coherent cuz I tried making a really detailed dynamic animation for reva's blowjob and gave up and redrew it cell shaded. I literally can't do some of this stuff with ai like the dynamic blowjob. For the art, I showed and explained everything possible in how it was made and how I did it specifically. I know the art looks like ai because people thought this type of art looked good and made ai base it off of that and that's fine. I am also one of the people that thinks this style looks good which is why I make it despite it being more likely to draw hate. If the problem is you think I'm taking away jobs from people, I am an artist, programmer writer for this and I still commission art, music, voice acting and more from other people so they're happy they get paid and keep getting to do what they like. I am just making a free game online to make people happy and from doing so I'm supporting other creatives in the industry to keep letting them do what makes them happy. I hope that's ok with you