[Karin Wells]

I intend to glaze the face and other skin exposed areas, the hat and the lace on the dress, the background settee, and the background.

When I begin to glaze, I do the skintones last. Of course you can get a "perfect" skintone early on, but it may appear to change when you introduce an adjacent color so I recommend that you do it last. Also, get the skintone exactly right before you begin to build light with opaque paint.

I also intend to apply 'velaturas' (semi-opaque paint, is this how one says this?)

I would call this a scumble.

1. How effective is my light and shadow for the whole painting?

Perfect.

2. How are my edges and light on the focal point?

For an underpainting, these are fine.

3. I am not sure how to glaze the hat and the lace, so that the dark 'holes' will show through...But, for glazing, should I glaze the shadow part with darker paint, and the light part with lighter paint, and then paint opaque for the holes?

Just glaze for color and be sure to bring the color glaze right over the holes. When you begin to build light in these areas, the already dark holes will appear much darker. Do not add darks until the end. Your photograph shows the darks to be much darker than they really are.

4. Also, for glazing, I was told to mix the paint with maximum of 20% of medium. Apply this mixture on the painting, and wipe it off with a rag, to get the glaze/transparent look.

I mix my paint with whatever amount of medium (Liquin, Galkyd Lite) that makes it as thin as I wish. I also don't use a rag to "take it off" as that is messy and you won't have much control in the small areas. I simply apply a delicate glaze over an underpainted area carefully and with a soft brush. To glaze an area into a jewel-like color, it will take many glazes - each applied to a dry surface.

However, if you are trying to "tie a painting together" with a "mother glaze"...you can smear on the paint/medium mixture and brush it smooth or wipe it with a lintless rag.