What is Glazing
Glazing is a very thin transparent layer of oil painting over an underpainting. We glaze when we want to alter or enchance some part of our painting, you can glaze with pure colors or opaque colors, it means colors with white in its mixture, but you need to be aware that an opaque layer it is going to cover more than a transparent layer.
A layer of glazing can vary its thickness some need to be very thin other layers have to be a little bit thick, it depends how much you can change the color beneath.
The traditional medium to thining down the oil paint is a mixture of turpentine and linseed oil in a 50 % ratio.
I use two brushes to glaze, both of them are synthethic with very soft and stiff hair, I apply the glazing with one brush and I use the other to fade the layer over the underpainting.
Sometimes you need to glaze to tone down a color other times to enhance some colors.
The old masters just to apply as much as 50 or 60 layers of glazes, the most interesting about this technique is the result, because it is for sure that the colors you will get would be imposible to recreat again without using this technique.
I hope you could find this video really helpfull.