Working with cold/hard waxes can be tough, we have found the method above to be the best and safest way to apply these waxes to your skis. We use hard waxes a ton here in the Midwest for training and prepping skis for other layers of racing wax. A good layer of green before you move onto your racing layers give you better wax durability and dirt mitigation.
Common cold wax application mistakes we see:
Too cold of an iron - we see more issues with the iron being too cold vs too hot, since a cold iron makes you move the iron very slowly across the ski. Set your iron to the suggested iron temp and make sure you keep moving along the ski, if it seems like your wax is not melting in you can increase your iron temperature slightly.
Too slow with the iron - when you move the iron too slowly the core of the ski retains the heat and keeps the base at too high of a temperature even when you continue moving down the ski.
Repeated iron passes to hit missed spots without taking a break in-between - the core material of the ski retains heat so make sure that if you are going back to iron a spot that you missed that the ski has cooled completely. Crayon more wax on any areas that are already ironed in to give yourself a buffer. (Missing a small portion of the ski is not a big deal compared to burning your ski bases)