Recreate a piece of art
If you want to learn to paint like da Vinci, why not learn from da Vinci? If you want to learn to sculpt like Michelangelo, why not learn from Michelangelo?
Pick a piece of art. Try to recreate it in detail. Reverse-engeineer the techniques used to create it. Fail. Try again. Repeat.
Imitate art for practice.
On the other hand — tools over technique.