OIl painting technique: alla prima or oil glaze?

Often I do a mixture of these two types of painting in my work. Alla prima, or wet-on-wet, means going directly from the palette to the painting - no scumbling, no underpainting necessary. The impressionists painted this way.

In this close-up of my current painting, you can see that the skin tones are prepared for glazing (thin layers of color over scumbled white), yet the girl's dress is being treated alla prima.

The skin tones are prepared by painting the shadows in bluish or greenish tones. Whites are enhanced, and after each layer dries, glazes can be applied.

During the Renaissance, Baroque, and Mannerist periods (among others) artists often painted in oil glazes. Examples: Titen, Caravaggio, El Greco

Both methods have their specific charm and can be used to create different effects in the same painting.