Definitely on the right track! One thing I'd work out is how hard you're squeezing the pick when you do this technique. You want both notes in the Power chord to happen at the same time, so it sounds like one seamless hit. Easing up your grip on the pick and letting your wrist/pick do the work for you will help with this. You'll know if your gripping the pick too hard if it crunches slightly into the individual strings one after the other and gives a slightly 'plinky sound' - or if you're feeling like there's a bit of resistance from the strings when you do your downstrokes -if that makes any sense
Was near the Guitar so here's a demo of what I'm talking about:
Hope this helps!