I like this one even better than your other one. I think that you are making the most of Paint and getting as good of an output as possible from there.
With that said, I would advise trying GIMP or Photoshop. I haven't used GIMP, but if it has any kind of brush tools, I think that you would be better off with that. Plus, you can work with layers and use blurs and other nifty effects like transparencies. I would download it and give it a try!