Can't speak to the synthetic without knowing what kind of material it is. For the leather however, it is pretty easy. If you are just trying to clean off some regular old compound that is caked on there you can get some WD-40 and a rag and get that off of there with a little effort. If you are looking to do a whole refinish, some sandpaper progression is what I normally do. Take the first layer of leather off with a lower grit and then progress up until you get the desired level of 'smoothness' you are looking for. Good luck