@mogu if you want to hold a conversation at people so they know you're talking to them.
And saying something it 'unbelievable' doesn't actually make it unbelievable, there's this thing called hyperbole.
Now as for medium change, I'm an artist myself who has switched mediums, so is my brother, and I know some people who have as well. Your knowledge of art doesn't just suddenly go away. As I mentioned before, people confuse simply switching mediums, with changing mediums as well as styles. Notice the thing Hotaru was good at was Matte painting, which is literally built off traditional art(since you work in the industry you know that) the character art, which is a little further from her style, she doesn't have results for yet. We haven't seen her carry over into 3D or anything like that. And matte painting was originally done by painting directly onto glass, all Hotaru would need to do to get good at matte painting is learn the tricks for it, and then learn how to use her painting techniques on a tablet(which she most likely practiced before she even got there cause she knew she was coming to work in a computer field) also as you can tell by their reactions, none of the staff is super familiar with matte painting, so their evaluation of the quality of it is not by an 'experienced professional'.
Which is the thing people are forgetting. Hotaru -knew- she was going to work here, she likely started practicing and learning before she arrived, so she's already familiar with working on tablets and PCs and probably learned how to carry over most her stuff already. She is no slouch, nor is she an idiot, she wouldn't have made the decision to work here if she didn't already have reason to believe that she could learn to do their kind of work, and that confidence would've come from study and practice before hand.
Learning the tools takes time yes, but it's not some daunting task until you have to change styles. Hell there are literally youtube videos on how to set up your CG program to work more like painting and many other things.
Edit: Also where are you getting you '15 minutes every morning' nonsense. We've seen Hotaru, if she is not doing something with her friends, she's painting. And for the record the clock on the desk, after Kou has already spent several minutes up, says it's about 6:10 in the morning. So we can assume Hotaru was up and out painting at like 6 in the morning that's more than just 15 mintues. And she does more painting than that throughout the day. It's just that morning that she spends -specifically- targeting the basics. She herself said she thought Kou was amazing because she "Doesn't do art outside of work" meaning Hotaru -does- do a lot of art outside of her 'work'.
And as well Kou does not say it's "only from hard work" she said "It didn't come out of nowhere. It's something she -developed- with hard work" meaning she took what she already had and refined and crafted it.
Edit2: And after rereading, Kou -still- calls Hotaru a genius (to her face I might add) not just a hard worker. So Kou is not saying "She's not a genius it's just hard work" she is saying she's "a genius that works hard". Also people need to stop taking Kou's evaluation as the 100% truth about Hotaru, Kou herself is a 'genius' artist who doesn't think of herself as one, so her opinion on what is a normal 'starting point' is skewed and she doesn't even know where Hotaru started, she only sees Hotaru's hard work and rapid growth. (in other words things Aoba or Nene have said don't suddenly become invalid just because Kou said something different, the truth lies somewhere in between it all.)