Help on removing crappy black paint please

I have a deadline of 10 weeks to get my caddy looking summat like a van rather than a wreck due to going self employed
the original paint was painted over with a brush and matt black paint
any ideas on how to remove the matt black and graffiti underneath so i am left with as much original paint as possible
i have no money either so needs to be done as cheap as poss

Nitrmous will get rid of it but may effect paint underneath also