Forcing is merely drawing your maximum everytime you channel. The White Tower guide novices very slowly while they learn, a practice which has earned them scorn from many cultures who channel. The Aes Sedai are merely scared that the initiate will burn herself out, so they discourage channeling at high levels - or even channeling at all.

The best way to channel is to be forced. You embrace your maximum every time you want to do something. It will get you to your potential quickly. Only an idiot will get burned out, and they shouldn't channel anyway.

Egwene probably did force them, and it's a good thing. She was forced and was stronger than Elayne and Aviendha for a good part of the series.