I don't understand how a hotwaxed ski left unbrushed could be fast in dirty snow unless the snow is ice or extremely abrasive. Perhaps liquids that are not adhered well to the base could be fast as they slough off, but hard wax? I really doubt it and suspect it might pick up dirt.
Adding also that structure is important in wet snow, but dirt loves structure. So I have heard, from my time in XC skiing, that the ideal structures in dirty snow are relatively simple so there are not too many intersections and corners for the dirt to get caught in. I have not tested this.
Adding also that structure is important in wet snow, but dirt loves structure. So I have heard, from my time in XC skiing, that the ideal structures in dirty snow are relatively simple so there are not too many intersections and corners for the dirt to get caught in. I have not tested this.