Fire with Flint

To test this fire starting method I bought two magnesium blocks with flint attached. The instructions suggest you scrape off a pile of magnesium from the back of the block about the size of a coin.
First I tried the $10 flint, and even with a sharp stainless steel knife I quickly realised that it would take about an hour to get a pile of magnesium that size. After I had a small pile I began trying to light it with a knife scraping the flint. I found the most sparks were generated with the knife perpendicular to the flint and by using lots of pressure. It seemed there was no way the magnesium would ignite using the flint.
I then tried the more expensive, $20 flint, which must have had magnesium of a different grade because it came off much more easily. The shavings formed curly and larger, they lit without to much difficulty (about 8 strikes).
Magnesium, for a metal, is very light, lighter that aluminium, so it blew away easily. Another potential problem is that when you scrape bits off they don't just land in a nice pile. Because I tried this on concrete I was able to sweep the shavings into a pile, but on most surfaces you might find in a survival situation, this would prove difficult.

One highly recommended survival fire starting method is to prepare cotton wool with some petroleum jelly (vaseline) and keep it in a watertight container. Cotton wool, if dry, will ignite very easily with a single spark but burns quickly. Petroleum jelly is difficult to ignite and will not burn well on its own. By mixing a small amount into cotton wool and leaving enough dry, fluffy parts which you can easily ignite you will have the best possible tinder to start your fire. It ignites easily, burns for a long time and will not easily blow out.
I was able to ignite wet cotton wool, with the vaseline mixture with a wet flint and knife. The friction between the flint and knife quickly dried them and the sparks eventually lit the cotton wool. It was more effort, and was definately longer, but in my opinion it seems the best option if stuck in the bush. If you store it dry, and begin to setup your fire in a sheltered place, either natural or improvised, you should be able to start a fire in almost any conditions. The hard part will be finding dry things to grow your small flame bigger.
What if you don't have pre-prepared cotton wool tinder? The magnesium burns so intensely that you should be able to light even slightly damp leaves. I found that it also burns fast, so fast that it dried out and burnt a patch of my tinder, but that burnt out very quickly and didn't start the rest burning. On the downwind side of a tree, I found some dry feeling lichen. This took as long to light as wet cotton wool, but was lighter and therefore blew away easily.

Over all my recommendation is that you buy a flint (they are quite cheap) and try it out at home with various tinder, including cotton wool with vaseline and decide for yourself how well it works for you. Consider available tinder in the bush, available surfaces to build a fire on, as well as weather conditions you are likely to encounter, and consider that you may have cold, wet hands or be wearing gloves.

.o Weigh up your survival needs with the risk of forest fire.
o Take all practical steps to make your fire safe.
o Have a lot of the driest possible tinder, kindling and fuel on hand before starting to light a fire.
o Pick a sheltered, dry place to light your fire.
o A bank, rock or wall of green branches will reflect heat from the back of the fire towards you.