I've tried this, hexamine only works well on damp wood if the wood is shaved out and used with dry tinder in my experience at least. I have burned out numerous hexy tabs with no result in getting a fire going on damp riversides unless preparing properly. They make great fire starters, especially on driftwood, but sometimes are a pain to light up.

Some homemade things I use: (remember, I'm not an ultralighter and I enjoy being somewhat of a pyro-maniac making homemade tinder)

*plastic bottle caps filled with parrifin with something to act as a wick inside
*tightly rolled newspaper (1" X 2" or smaller) tied with twine and dipped into parrafin
*old-school tuna can-trick: card board strips curled inside can, add a string, then fill with parrafin. I found these also work good if I run out of fuel tabs: I turn the esbit-type stove upside down and put it underneath. Boils water in a stainless mug right away, but with nice and messy residue
*buffed-up cedar bark I always carry. Eastern Red Cedar grows everywhere where I live.
*Char cloth

I've had my fill of magnesium fire starters, like DR says, its hard to keep the shavings together, so I roll pj-soaked cotton balls in the magnesium shavings. Took this tip from this forum. These take a spark on the first try every time for me with ferro rod or Spark-Lite (at least in dry conditions) AND burn for at least 9 minutes

Again, I advocate Coleman fire starter sticks, cut twice the size of a bullion cube, burning about 5 minutes.