Best tool to clean/remove years of oil/dirt buildup?

If you have a place to do it off driveway,or yard, i used kerosene in a garden sprayer on a portable kwicklift, just spray enough without it dripping or running everywhere ,with a garden sprayer, soaked it and let it set over night , 3 times, then used a pressure washer, it took grease ,oil, mud and old undercoating off. About $20 on kerosene and $20 of simple green degreaser.