paper towel or shop rag is sufficient.
the amount of fuel depends on how long the truck has been sitting.
if 5 minutes of less - it'll be fairly strong squirt at about 49 psi.
if longer, then its significantly less, all the way down to 0.
just cover it with a rag, press the little valve with a screwdriver, and don't let it hit you in the face.
AND DON'T SMOKE...