All refinement means is that you've produced an experiment or two and are able to identify what went wrong or could have gone better now that you've done it. Then you produce evidence that you can improve one or two aspects of that experiment and then analyse how this experiment is better than the last, that's refinement.
Use different materials including paper, paint, brushes, etc. I would recommend (from a high grade art student) doing monoprinting on tracing paper and even wax on fabric then ink for colour