After my episode on pizzicato, I got a lot of questions about left hand pizzicato, so I decided to talk about this technique. It is a tricky technique requiring a lot of strength in the fingers.
I find it helpful to think that plucking involves a kind of lever principle: the closer the plucking finger is to the finger playing the note itself, the more difficult it's going to be (and the harder you have to pluck - a short lever in other words) - while if the plucking finger is further away, it's as though one is pulling on a long lever - it feels much easier!
Making the pizzicato even is not only a timing thing but also a question of identifying which left hand pizzicato notes are less audible. You'll have to use much more force on certain notes than on others (usually depending on how close the plucking finger is to note itself). So listen closely to yourself and identify which notes need to be plucked extra strong, in order to sound as clear as the others.
Some left hand pizz. passages alternate between using the bow and plucking with the left hand (for example in a lot of Sarasate's music). I find this type of left hand pizz a little bit easier than the passages that are entirely plucked (with both the right and left hands - like in Ravel Tzigane and Paganini's 24th caprice).
In order to avoid injuries, when you start practicing left hand pizz it's important not to go too crazy right away, to take breaks from it and build up stamina gradually.