And a small amount of methylated spirit. The meths burns cleanly to heat up the vapouriser to get it started and leaves no soot.
Fill the main container with paraffin to about 3/4s full, not full to the top.
In the centre of the container at the top is an annular depression that will hold a few cc's of meths. light the meths and leave it to burn almost till its finished, then start pumping the plunger. BE CAREFUL THE THING COULD WORK LIKE A FLAME THROWER.
It means that the vapouriser is not hot enough and you will need to start again with more meths in the annular depression.