I watched the show and found a pose that looked nice, then sketched it out (in scraps). The head was by far the hardest part to capture the MLP style of, even after looking at a ton of references. Things like line thickness and tapering are super important too.
And yeah, Flash was ideal for this, as it deals with vectors just like in the show. Means you can resize/change things without distortion, helps make the lines smoother and you can separate/animate the parts if you wish to do so.