The DLC can be beaten in under an hour if you speed through it. You shouldn't do that on your first play through. Enjoy being Chris Redfield.
Don't unload all of your special handgun bullets in the new white molded. One bullet makes them weak to other forms of damage, even the large ones. Shoot them with one and then switch to something else.
The head boss is pretty tough. The more special handgun bullets you can have for it the better.