The Altberg Ledergris is the best thing I've ever used on boot leather, their bumpf states that they've developed it as a more suitable form of Dubbin, which works much better on shoe and boot leather that's been tanned using modern methods, and in use this has, in my experience, proved to be the case. I use it on all my leather boots with great results, and I do it exactly as they recommend - one brush, use sparingly and just keep on brushing vigorously 'till it's soaked into the leather and the wax begins to coat the surface.................never had a problem.
I think it's a blend of oils and waxes that seperate out under the heat and friction of the brushing - the oils soak in and the wax sits on top.............works well for me!.....................atb mac