We've seen very simple weaves, such as shells of hardened air or fireballs sliced and compared to balefire, these are much quicker and easier to channel.

Considering Rand caught himself and his friends with a cushion of Air while falling, has erected his shield right before an attack hits and caught an arrow before it hit him, channeling can be very quick, depending on the skill level of the channeler and what they want to do. Nynaeve had her own airclub weave sliced by Moghedien almost instantaneously from the forming and aiming of it. Almost instantly, Moghedien had a weave of Compulsion on her, and Compulsion itself is a very complex weaving of flows. And we've seen various techniques for slicing weaves in the books, so it seems that depending on how much power you have available and what your strength level is at the moment, the more experienced channelers had a number of ways to counter threats.

So slicing the flows of a weave, especially as one as complicated as balefire, seems to be more about your nerve and your speed.

BTW We've never seen balefire erase flows. This was why you can't just balefire a complicated weave to get rid of it. Balefire seems to only work on physical objects and the souls of living things. Otherwise, Bel'al would have just directed streams of balefire around Callandor to release it.