Just a small point, if you have your sim write children's books it is surprising how quickly you can supermax writing. Although it is not obvious if you look at the given book length, they are actually significantly quicker to write. This means writing a lot less to complete the supermax challenges, and a higher chance of writing bestsellers etc. Also, If you have WA you can go abroad and write 95% of a "Masterpiece" while on holiday then complete the last 5% (for full career progression acreditation) when you get home. Obviously, children's books get the lowest royalties, but the shear number that can be produced in a single session easily compensate for this.
The same priciple applies when trying to supermax painting, paint only small pictures until you have completed the challenges then switch to medium or large if you wish.