This method disconnects it from your normal language processing. Start by learning simple words so you associate it with your language. You'll be at 20wpm no time.
I was taught that you should learn at speed (~20wpm) with 2 characters and build from there.
Looking in to it, I see there's two ways - Farnsworth & Koch. The downside of the former is that you get stuck with slow speed and have a harder time to get faster. The downside of the latter is that the initial learning process seems more pointless because there's no actual words.