If it's new paint rub the next day or it gets too hard, sand first with 1000 grit then 1500 then 2000 besure to sand out the previous scratch before going to the next grit,this makes the surface flat before buffing, use 3M 6060 or simular compound.
Use a polisher at a very slow speed 1800-2000 RPM and mist with water as polishing do not use heat as done on old style paints !
If it's factory paint use only very fine polishes since the paint is very thin and do not sand.
