Sounds like a plan, fleshing out the anubias. If you can lay hands on smallish rocks, what works well (according to Amano-san) is to attach your epiphytes to small rocks then tuck the rocks into hollows in the driftwood.
Something I have been thinking about is to get some of those washer shaped stone beads, use those as anchors for the plants, and then screw them to the driftwood with brass or stainless screws through the holes. Course, you could probably just skip the beads and use screws, but where's the fun in that?
Java Fern takes lots of patience, I have found. I am just now, after 2 years, getting some acceptable growth on the ferns in my 75.