I think your first question has been answered "no follow= no PR effect"

I do not think more content is the answer, it rarely generates external links unless you are in a writer, tech or design field, like the billion bloggers blogging about blogging.

As to what next, one there is a large do follow movement in the blog community, check their comments using one of the browser extension that highlight no follow links. If do follow use them.

Many blogger are open to guest posts with bio and links; might be 2 or 3 times the work of a good comment but I think it can be worth it.