If you ever decide to clean your paintings you can try this easy way to have a good result.
For this action you'll need:
1) A soft bristle brush.
2) Unsliced doughty bread.
NOTE: Never use water or solvent to clean paintings! If it's an extremely valuable or an antique, you can use a professional! :-)
After you start, as you can see in this video, imagine, while using the brush, that you're dusting pollen from flower petals :-)
Good luck from now and enjoy the result!