I am trying to install an Oatey Shower Drain. The drain comes with two washers a fiber washer and a rubber washer. The question I have is how to install this drain in a fiberglass shower stall base. Which order do they go in and should I use plumbers putty at any time during the install? Does the rubber gasket go between the drain base and the shower base and the fiber gasket on top of the shower base and under the screw in drain top? Help...