Fire is crucial. My experience has been that those who can build a fire, survive. Those who can't, don't.

Keeping a fire going, once it is started, is trivial. Before long, the glowing bed of coals will ignite rock. You can let the fire flicker out, throw on some more fuel, and away you go..

If starting a fire were so difficult that I would need to consider carrying glowing coals, I would seriously reconsider the decision to travel. It could easily be better to stay put, rather than travel.

Usually you travel to improve your situation. In the mountains of the western US, a very short trip will put you in a different environment, typically warmer and drier, with greater ease of fire building. If I could not anticipate those conditions, I would stay put.