last weekend I printed three Marvins: 1x Bronzefill, 1x Brassfill and 1x Copperfill. After printing they were pre-polished for approx. 8 hours in my self designed rocktumbler and finished with a buff wheel. Not perfect yet, but the result is ok for a first try
The lesson I have learned is that I have to print finer layers to make polishing easier - will try it soon.