Being totally ignorant in fire starting methods, I too had doubts about Coton + Vaseline.... until I actually tried it.
As Minime said, it catches sparks very easily and burns very well.
Stored into bits of plastic straws, it's very simple to put in a PSK.

So, just try it ...!!!

Another, more bulky item that catches sparks very well is the gel sold with the the Firestar type cooker.


Alain