In reply to Stephen B I'm afraid there's no quick way to treat them. But the most efficient way that involves using crown down technique with orifice openers first, then a size 8 hand file followed by Hybridization of Tapers (sizes 15/05, followed by 15/04 followed by 15/02). Each file is used only to engagement using either SSC (one stroke each) or Rhythm Motion (3 strokes each to engagement). The key is not to push, have a super light touch, and engage for only a fraction of a second before backing off. The goal is to gently follow the path created with the 8 file (after orifice opener). Using this cycle of hybridization one tapers you'll get down easily (as long as you have a patent canal to a  size 8 hand file). 

In reply to Stephen B That's a great question Stephen. You can probably do either sequence and get the same results. The Booster Tip on the ESX helps combine size 25 and 20 in the same file. But obviously, I always say if you use 3 files to do the job you will distribute the job between 3 and therefore will be safer, but you will be a little less efficient. So, you have to decide what's your priority, safety or efficiency. People have been pushed towards efficiency recently which is why the ESX sequence was developed. But for the longest time I used the 40-20 crown down technique with SSC and it was the safest technique ever. In order to increase the efficiency of several files I used multiple handpieces. But most people don't want to invest in multiple handpieces and therefore ESX was developed to give them less files using less handpieces.
But I want to reiterate Dennis' point here about time of engagement during hybridization of tapers. It's very quick engagement. Time is of essence. The file touches the dentin for less than a second during engagement at all time. That's key point for safety and something not explained enough by educators. Should be a Friday Question! ;)