I just went and played a few co-op bot games after watching the video below. Try to remember as many combos as you can and chain them together.
I'd say you'll need several games of practice to start really "getting it," but once you hit an awesome combo that damn near wipes the opposing team, it makes the work worthwhile. The easiest one for me to regularly perform (late game) is tornado, meteor, sun strike, deafening blast, and then whatever you need after; usually cold snap or ice wall if you don't have a refresher.