I bought 2 bottles of the light and dark wash from Sprue Bros. When applied over a cured base coat of Future, it is very easy to use and clean up. Each bottle is supposed to do about 12 1/48 kits.
For me, It is much easier to use this product, than to do the old trial and error method of home made washes. Some veteran builders prefer to blend their own washes, but I find it frustrating. Pro Modeller's pre-mixed weathering washes are a great time saver that also deliver great results.