@Pooky21365 Yuni's starting traits were Cheerful (because Cheerful begets Happy and Happy boosts everything else), Creative and Music Lover (because Music Lover allows her to get Fun from listening to music). I kept music on all the time, unless she was trying to sleep. For some reason, Sims cannot sleep with music on.
Since it worked well with Yuni, I decided to keep Serenity similar. Her initial traits were Cheerful, Creative and Genius. In addition to being a painter, Serenity was an author, so I figured Genuis would help with computer work.
I wish I could remember what level painter each was when she painted the big-value pieces. I don't think they were level 10, though -- I'm pretty sure it was before 10.
As soon as I could, I bought each of them Creative Visionary and Marketable. Those two traits really helped.
@katoregama Thanks! I like the leggings look, too (even though in RL I can't bring myself to do it! You're welcome, society :p). As far as stuffing stuff into mini-homes, my next painter has been doing mostly smalls recently (except when required to do Emotion paintings for Aspiration). Since you can fit 6 smalls on one panel of sheet-rock, she'll be able to fill even a tiny room with lots of visual interest. Hint hint for the 4x4 Challenge... :p.