Preparing for wildflower seed sowing

I just watched last Fridays gardeners world and was inspired by the Somerset field of dreams. I would like to prepare a small bit of grass with the newspaper mulch method. My first question is what kind of mulch should I use and do I just dig all the newspaper and mulch in before sowing or should I remove it and then prepare what's underneath it for sowing? Second would I have to do this every year or do the wild flowers self seed. Thanks. Anna