I have used a small scrap of artists watercolour paper and poured out three samples. Each sample has been 'watered down' with plain tap water to see how it behaves when diluted.
The Mahogany Stain first; The colour conforms to the packaging, having a dark almost berry colour. The Oak Satin, when diluted reminds me of the old (very old) Games Workshop Flesh Wash - the one that came in the blue-topped bottle. Finally the Walnut Stain, which is a very good substitute for the Devlan Mud wash. It is less concentrated than the GW washes but when applied in layers gave a similar effect.
I have used a diluted mix of both the Mahogany and Walnut Stain on both the walls (over grey - Skull White and Chaos Black) and the base (over Snakebite Leather) of this simple piece of scratch-built terrain.
I am less confident using it undiluted, but will certainly use these stains on my terrain keeping the small GW pots for figure painting.
I hope that this short review helps. I am not sure where you can now buy these products - as I stated above they were bought cheap and as a clearance line. It is possible that they would be easier to source in the US.
I have seen that these Folk Art stains are available from Amazon (amazon.co.uk) in the UK