the Bob Moore pen is a tiny tube nib under a reservoir which holds a few drops of paint
it fits into a swivel head on a handle
it uses ordinary enamel paints thinned slightly with lighter fuel [eg Zippo] to make it run smoothly
its a bit fiddly to use and has to be regularly unclogged and cleaned out with lighter fuel
with a bit of practice its ok to use
here's a link to the supplier's website
http://www.phoenix-paints.co.uk/misc.asp
yes I think its worth the money - with the cost of the pen, paint, lighter fuel, syringe, masking tape its still less than having one engine lined professionally
and I can use it again