As an alternative to stirring, you might want to check out the article by Jeff Renner from the Mar/Apr 2010 (or maybe Jan/Feb) issue of Zymurgy titled something like "pseudo decoction mashing". Basically, it's a way of using a pressure cooker to do your decoctions and it requires no stirring. I've been using that method and am very pleased with the results (and happy to not have to worry about stirring or scorching).