For glazing I dilute my OPEN acrylic paints with Golden OPEN Acrylic Medium (Gloss). The ratio of paint to medium determines the transparency of the glaze. I find glazing to be particularly effective in skies. The multiple layers of pigment appears to mimic the multiple layers of particles in the air, providing a transparency and depth to the sky not attainable with a straight application of paint.
Note in the Initial Version below, the sky cloud and sky shapes are established, but the sky appears somewhat flat with not a great feeling of depth from the top to the horizon.
In the Intermediate Version 1, glazing has been added: a white yellow toward the horizon, a purple underneath and within the cloud, and a warm red at the top of the sky. Now the horizon and the bottom of the cloud begin to recede, the cloud has more form and the top of the sky is looking warmer and more colorful.
In the Intermediate Version 2, there is more of the same types of glazing, with the addition of yellow within the cloud to provide form and warmth of the setting sun.
In the Final Version, the glazing further punches up the effects started in the previous steps. Particularly more yellow/white glaze was used in the lower part of the sky. Some yellow glaze was used to neutralize some of the purple under side of the cloud and provide some warmth. Additional yellow glaze was used in the sunlit portions of the clouds. Additional warm yellow glaze was randomly applied to the top of the sky and brought down into the top portions of the cloud.
Note also that in each stage warm glazes were applied to the sunny face of the Met Life Tower, to reflect the warmth of the evening sum.
All of these glazing efforts have resulted in a transparent sky and clouds that recede towards the horizon, and serves to help pop the dramatic shape of the Met Life Tower.