ive been told old engine oil is the best because it has carbon in after being burnt.
Vasoline isnt that expensive, there are lots of cheap makes, £1 shop for instance you get a large tub of it, just smear it on, its good because its clear and can go onto panels, i put it under the wheel arches and just smear it over eveything underneath.
Also its good to put it in the spare wheel well, wouldnt advise getting it on your spare tyres though, i think petroleum jelly rots rubber.
Chris