A little late, I know, but I’ve used the pink undercoat on a couple of miniatures and am suitably impressed.
Both miniatures primed white. All colours from the Vallejo range and were brush painted. Photos aren’t great, but show off what I mean.
Horse cloth on the right was done conventionally. Pale sand underpaint with ivory white highlights, then three layers of yellow ink overpaint.
Horse cloth on the left was under painted with one coat of old rose then overpainted with two layers of yellow ink. The old rose allowed the undercoat to act as highlights.
There is a much better depth of colour to the pink underpainting in my opinion. It’s certainly the method I will use going fowards.