Piet,
Then I would say you're on the right track.
Andrew Wyeth tells a story of his own training by his father, who had him draw a skeleton he had on a rack, every day, which young Andrew regarded as drudgery. One day, N.C. Wyeth took the skeleton and locked it in a closet, where Andrew could not see it, and instructed the boy to draw the skeleton, whereupon he found that he could do it from memory.
Norman Rockwell related a similar account of his training with George Bridgman, who insisted on his students drawing the skull from every conceivable angle, over and over, until they could do it from memory. Rockwell said he and the other students considered it excessive at the time, but that in later years, as a professional artist, he realized how valuable a lesson it was.
Virgil Elliott