Obviously ‘oil glazing’ is an oil painting technique! Start with a black and white painting (grisaille is the technical term!), wait until it is dry then add blobs of translucent oil colors, spread the blobs over the areas you want them and wait until that area dries, then repeat!
You can remove some of the oil paint with paint thinner and then glaze over the area too! Makes an easy way to create a night sky with stars!