I am going to mulch my berries too, as soon as I get more mulch. I use shredded computer paper for mulch. I get huge bags of the little stuff at the side of the road in the commercial district of town on recycle pick up day. It's free, lightweight, clean and easy to use. It just looks odd because it's so white, but I don't care what color it is.
I used it all recently and need to do another drive through for more on Thursday evening.