Foundation and concealer help?

i use maybelline dream matte dark caramel foundation, it covers up dark spots on my face well. however, i have a problem with it not covering my birthmark(on my chin). can a concealer do heavy coverage?? which maybelline concealer works best? and out of these foundations, which one has more coverage and lasts longer? MAC or Maybelline? i put on my make up at around 7:45-8:00 and finish at about 8:30 every morning right before school(8:45) and i dnt get out til 3:45, how do i get dream matte to last these whole hours?