When teaching mathematics I like to always mention that the greats like Ramanujan, while it seems like they just knew everything from pure thought, they all actually did a ton of work by hand. Ramanujan in particular is known for his fastidious notebooks calculating thousands of digits numbers like pi. From writing out the calculations for hours and days, he'd come up with simplification formulas and develop new insi…
However the kind of work you’re discussing doesn’t match my understanding of “busywork”. Busywork means unnecessary work done to give the appearance of actual work. Busywork doesn’t produce much value beyond appearances.
The work you’re discussing is “the work”. It’s the underpinnings, the research, the practice, the artist’s sketchbook, the exploration, the learning. None of that is “busywork”. If anything, it’s the opposite. Much of it will look like busywork (i.e. bringing little value), yet actually producing the highest value in the long run.