+1 for Alpinord's rec of Maplus Race Base Hard (or Swix CH4 which seems similar -- http://www.racewax.com/product/FA-3681/SWIX_Hydrocarbon_Wax_CH4_180_grams__FA3681.html
). Superhard and hard to work with == as noted scraping/brushing is key and is tough with these products. Couple of shortcuts that have worked for me in cold eastern conditions with abrasive snow are:
-- turn up the iron to get the hot stuff melted and absorbed.
-- apply as thin as you can and do a light scrape while still warm, to avoid having a thick impenetrable crust to take off when fully dried.
-- first wax a light layer of your normal wax tip to tail (in my case, green RaceWax HC, or an all condition Toko HC), and then drip the
Race Base Hard or CH4 at the center of the ski and along the edges under your binding. Even just mixed with a regular wax, the hard stuff helps slide in the cold and will maintain durability on abrasive snow
-- same as above but instead of using the hard stuff in block form, sprinkle on the powder equivalent: Swix CH3 cold powder (http://www.racewax.com/c=NPYGGbHkzLjmFtFeCID0CGn9z/product/FA-1216/SWIX_CH3_Cold_Powder_Ski_Wax__FA1216.html
) or Toko X-Cold Powder (http://www.reliableracing.com/detail.cfm?edp=10319879
). Someone recommended breaking down a CH4 block with a cheese grater but I couldn't get that to work properly with either CH4 or the Maplus race base; it wasted a lot of wax and it's easier and maybe cheaper to just get the powder product to start with.
-- Last but not least: rotobrush is your friend. I just got one and the brass brush just kills the CH4 type stuff -- 60 seconds and done much better than 10 minutes of hand brushing.