Actually what started it all for me was Gospel drumming and noticing how those drummers would always have a hand diddling on the snare when doing fills. Then one day I came across a member here by the name of David Floegel and this video here:
Doing this exercise slow is fine, it's when you started to speed up the diddle on the left hand is when it became tricky. Gospel drumming, this video and more like it have opened a new door into drumming for me.
Or like this video here by Adam Tuminaro who is an awesome drummer and teacher. These kind of triplet fills are what inspired me to work on my left hand as you can see there are a lot of diddles on the left hand.
I'm now trying to do triplets on just my left hand and trying to work on continuous diddles on my left hand.