I just have a screen at the bottom of my kettle. I let the grains steep for about an hour, check for protein then open the valve. Sometimes recirculating is required to ensure all the grain is filtered out . To make sure I get all that grain goodness I run several gallons of hot water over the grains and collect that as well. I feel that this is easier than a bag but thats just me. So... I guess you'd say I use a strainer also. All that being said a Lauter Tun is a grain strainer.