Learning to produce quality articles quickly is a skill that most webmasters chase. And I don't blame them, as the more articles you create and submit online the more traffic you generate to your web site.
At the time of this writing, on average I create 10 articles per day. If I am feeling energetic I can produce in excess of 20 articles - but that doesn't happen very often.

Something that really helps me is my typing speed. I reckon I type at about 80 words per minute and so that probably has something to do with the quantity of articles I produce each day.

I suppose the second thing is that I no longer have to do so much research as I did in the early days. Most of what I write just flows through my finger tips and although I am always learning new things, the amount of research I do now is minimal.

Basically if you want to improve the speed at which you write your articles you are going to have to keep writing articles. The more you type the faster you will become over time. When you feel comfortable writing articles you will know that you know your topic inside out and the need for continuous research will diminish.

You could also write shorter articles. Once, one of my subscribers wrote a 1,600 word article and wanted to submit it online. There is no need to write an essay. A 300 - 400 word article should suffice.