I often suggest writing every day. I'm not, however, unfamiliar with the difficulty of living up to that dictum. It takes discipline and effort. It takes writing at inconvenient times, often when you're tired. It's still a good practice. And if you want to write, whether as an academic or simply because you think you want to be writer, you have to write every day; you have to have a disciplined practice. I don't know of any writers for whom the writing came easily. I know plenty of stories of writers working hard and regularly.
The blog is an interesting form in that a large part of what makes a blog work is that it has constantly new information, that it is constantly updated, like a news outlet of sorts. It's a form that calls for writing every day, and therefore it's good practice for me--as a writer who gets out of the habit.
I suppose it might be considered a form of procrastination, in that I have other writing projects that have, perhaps, more pressing agendas. But, on the positive side, inasmuch as it helps me get in the habit of writing, and gives me practice in the difficult task of putting my ideas into words, as well as the opportunity to dabble with the nuances of language, the little alterations of voice and style, it is procrastination that helps me in the long run. I think.
And sometimes I think that older modes of publication are of less importance now, anyway. Do I need a publisher and publishing house if I can write something that reaches people over the internet? Of course the publisher gives a certain credibility to the work, but is that credibility any less than the credibility of having an internet readership? To the best of my knowledge, I have no real internet readership at present, neither do I have any publishing contracts. So maybe writing a blog is just as credible a way to write as seeking a publisher. Both courses of action have potential upside; both courses of action require effort. I write partly because I find that it helps me clear my thoughts. But mostly I write because I think I have ideas that would help other people--I want to reach people with my words, just like any other writer.
Ultimately, I can't prove it, but writing everyday--in whatever form you choose--seems to be the way to improve as a writer. Of course choice of form affects what you're familiar with writing--but the skill in writing is one that translates from task to task--the task may be unfamiliar, the forms unusual, but nonetheless the basic task will be to capture your ideas in words. And so, if you want to strengthen your writing skills, write every day.