oh peyare bhai , compounding little tricky better get any professional experties for this process , specially black colour require extra efforts to make perfect finish while compounding and best results of compounding comes by rotery polisher
about sonex polish its colour coded polish and its having masking abilities instead of much cutting but yes for time being it will produce very good optic and deep black colour
if u like to do it urself than better first go for mild products like mother 3 steps