Not a recommendation so take it on your own, but I've used box
fans to evacuate fumes when spraying aircraft dope in an
enclosed building. Dope is basically lacquer, and mostly
lacquer thinner.
Box-type window fans and all centrifugal blowers generally all
use shaded-pole motors, which have the starting winding wired
in permanently and no starting switch to make a spark.
The only fear I would have with a box fan would be from static
build up generated from friction or from the manual switch. I
would make sure I had a ground wire to a good electrical ground
point and turn the fan on before beginning and after the fumes
have cleared.
If you're going to start painting things on your truck
then it's time to visit Harbor Freight and pick up a
cheap $20 spray gun. Stop by your local automotive
paint supply, many autoparts stores now carry a line
of automotive paints, and pick up you paint. They can
mix you up a pint or even a half pint. Shoot it out
side and you won't have to worry about a box fan but
do wear a respirator and stay upwind.
here are a few pictures (click next) of the wheel I
sprayed as described several years back with
PPG Omni. Handled for 10,000 miles so far and it
still looks like I just installed it:
http://www.pbase.com/dennygraham/image/116022024 DG