My approach is always analytical - first the drawing, then a groundwork of faint colour, then light preliminary shadows and shading, followed by more defined colour, more intense shadows and shading, layers of transparent glazes, until the whole approaches a finished state. Hours slipped by and bars of sunlight moved across the table - my ideal studio would have western exposure for a longer visit with the sun - and still the snowdrops needed details, the green markings inside the bells of the flowers, the fine stripes on the leaves, and beads of moisture here and there.
There is never enough time in a two-hour art class to get to this final polished state, except in a very small painting. And art teachers never tell their students to paint small!