I mostly use shaving foam pies on paper plates which is exactly what you don't advise. I have put shaving foam in a pie plate. In addition during the summer I put a real custard pie in my face, a real whipped cream pie in my face ( both with pastry and in tin foil pie plates), a squirty cream pie in my face (in a tin foil pie plate) and a real banoffee pie in my face (on a paper plate). I have also used other real pies. I like shaving foam because it's easy to clean up the mess.