If your deep-fried fish is greasy, then make sure your oil is between 350°F and 375°F the whole time you are cooking the fish.  Don’t let the oil drop below 350°F when you are putting the fish into the fryer.  Adding the fish slowly and in stages will help to eliminate the greasy outer crust.  Use clean unused paper towel that is lined on a plate to place the deep-fried fish onto after it comes out of the fryer.  This will help soak up any excess grease.