how do you make the fashion posts? you must have designed hundreds of outfits at this point
I liken it to drawing trees. Hopefully I can make that make sense. If you sit down and draw a lot of trees of different kinds, or plants, you remember that stuff later and the variety starts to fill itself in after a time. It's like learning an alphabet, but limb and leaf shapes, I guess.
I have a lot of fashion books, but not like fashion catalogues. I have books like Folk and Festival Costume that are hand illustrated. Seeing someone else capture fabric weight and folds in lineart has been a huge help for me, and there are lots (lots) of fashion books that do that. Kinda like how there are a lot of art books took talk about lineart techniques for plants. If you're an artist and can't get books outright, I think internet archive lends digital copies.