Repaint masonry window sill

Our house has a Victorian bay window and what appears to be chunky masonry/concrete window sills. They look like they are painted with some form of gloss which has become flaky and green over the years.

I want to repaint it and after either stripping or sanding I want to know what paint to use. I was going to buy some good quality masonry paint to use to paint the walls of our house (combination of brick/render) and wonder if I can use the same paint on the windows sills?

But masonry paint sometimes looks thinner than gloss paint and I wondered if should I buy some proper masonry gloss paint (if that exists?)

Thanks.