New snow crystals in this temperature range and with medium to low humidity are like a million tiny knives to your ski bases. Kinetic friction is the main kind of friction to deal with. This means hard, durable waxes that keep the sharp knives of the snow crystals out of your ski base is what you need. Any other water or dirt-repelling compounds will help your glide, but not to a high degree.

Kick waxing is dead easy in blue conditions. Hardwax sings. If you're skiing over 15km, use a base binder, but aside from that, it shouldn't be too hard to find a hardwax that gives you good grip and glide.