Artpassing can be intimidating as it starts to "solidify" your blockout, as well as being your map's first impression. If you're looking for some initiative, I recommend looking at this thread:
https://tf2maps.net/threads/art-pass-club.49495/ It contains small pre-built gameplay spaces that task you to artpass it.
I did a few myself and it feels great to let go and paint a room how you're imagining it without worrying about how it plays. I'd also recommend giving yourself limited time to do so (I've done an hour time limit, you could try a day or a week) , so you don't get hung up wanting it to look perfect. Give it a try, start small and work your way up to build confidence, the main thing is to have something to show for your efforts. If you want further hand-holding help with detailing, I can offer my personal tips on your project, feel free to ask.