There is a way to speed up sculpting, though it is in fact cheating. It's actually rather simple. Buy as many sculpting stations as will fit on the lot but will allow your sim to still move around. Now, one by one, have them start a clay or ice sculpture, and as soon as the block appears, cancel the action... Move onto the next. The game decides what will be sculpted when the action begins.
Once all of the sculptures are started, type in "moveobjects on" and "testingcheatsenabled true" in the cheat window. Go into buy mode. One by one you can pick up each block to "reveal" the sculpture inside. After you've determined it is a sculpture your sim already knows, hold down shift+ctrl and click on the block, selecting delete object. That part is important because if you DON'T know the sculpture and delete the block, the sculpture will be forfeited. Repeat this process for the whole lot of stations. Then, one by one delete the sculptures as well. Now, if there are any sculptures your sim didn't know left, go back to live mode and have them continue those ones. Once done, start again... Later, rinse, repeat. Not QUITE as time consuming, but it can take a while.
