Different materials, different techniques!
In order to paint on a canvas, panel or wall, an artist must master every technique. Painting on canvas means using a soft media with a fairly smooth surface.
Panels, like the one of St. Albert, are hard, made of wood and very irregular, and can have higher and lower sections. Finally, in order to fresco a wall, an artist must lay out an even base to achieve a smooth surface on which to place the colour.
For any painting to be successful, an artist must, therefore, have excellent knowledge of the technique and materials.