M101 has been industry go-to for detailers for a long time, especially in Europe. I use this when I need a sledgehammer: it's a pretty aggressive compound but works great when you have something really rough to tackle.
I like to use it with with the Meguiar's microfiber cutting pad on a dual action polisher but you can use it with a foam cutting pad as well. The only downsides are the smell and the amount of dust it makes. You'll need to blow out the pads fairly often.