I do use it a little Buff but… sharing my big secret here… my main way of capturing the Umbrian stone is a mix of these three colours with a lot of water.
I’m currently testing Roman Szmal’s Aquarius paints so have written my usual DS colours as well. This mix gives me much more colourful and granulating and separating washes than I get with just using buff.
Are you a big Buff user? Have you ever tried to mix a similar colour from other paints in your palette?