I've tried their Soil and Tarmac/Concrete ones and they are excellent. They dry rock hard though so if you get a bit where you don't want it get some water on it and take it off before it sets. The hardness of the finished product has advantages though- unlike mud etc made with plaster/filler dust the Tamiya stuff won't flake off at the touch of a brush so you can hit it with washes, pigments etc to blend it in and give it more tonal variations. Can't say I've worked with the Snow one though and I wouldn't recommend the Grass one.