I am playing it on hard, and the secret is the same as medium or easy. Stay low, take cover, and pray to god. Well not so much the easy and medium levels as the hard. But I can make it to the shingle without using the medic, bu make sure if you are having trouble just run to the medic, he'll heal you. Good Luck then.
------------------
"God I hate Nazi Trains ever so Much!!!"
"The Only Time You Worry About A Soldier Is When He Stops Bitching"