Most important is weather the paint is oil or water based. As a line
painter we use both as do highway crews.
A) The difference is oil based paint can be removed with a good solvent or
road and tar removal product. Do only the area as needed and flush with
water immediately.After this wax with a good paste wax to restore the
paint protection. Waterver u do check /try out a small area first to make
sure you are not removing the van paint as well, never do this on hot
metal and make sure the area is well vented. Wash and wax afterwards is
very important. Cleaning the inside of the van is optional..lol

B) For water based paint the removal is more difficult becuase of the high
soilds content of the paint. It also has a tendency to dry like cement or
cooked oatmeal. Soak the area with warm or hot water for a few
minutes,repeat if the stuff is really caked on ,then apply a mixture of
pine-sol and warm water and scub gently with a light brush. You may have
to repeat this several times before you get the paint off. For some reason
the pine-sol formula works to break down with the amonia in the waterbased
paint. We actually use Pine-Sol to clean our paint machines so the dont
clog up. Ive been using this stuff for 20 years.

If A and B dont work a good body shop can probably buff off the paint but
this will cost you. Good luck.