Picking a curtained lever lock using a curtain pick is a very skilled process. In my opinion, it is more difficult to pick up and learn that pin tumbler picking. That said, even curtained lever locks can be picked just using 2 wires. Very broadly speaking, it is the curtain itself usually throws the bolt. There are exception to this, of course, like the old Securefast, whose curtain will spin freely when tensioned and it is the key itself that throws the bolt (like a traditional lever lock).
The curtain pick is certainly not the only way to open curtained lever locks though! They can be opened via: picking, pin and cam, impressioning, self-impressioning, visually decoding of lever bellies, visual decoding of gates, reading the backside of the lever bellies, Plasticine belly reading, bypass (works on most)...a million ways to skin a cat and all that...
If you want to know more about any of the techniques I listed there just let us know, I love working on lever locks.