BS suggests a mash in with 14.64L of water for the 60min mash, then a "2 part" batch sparge with 4.23L & 13.44L.

I assume I add the first 4.23L to the mash as soon as the mash is finished, then drain the tun to the kettle, then add the other 13.44L (I give it a stir an re-lauter) then drain again to the kettle.

Is this correct? or do I drain the mash tun, then add the first 4.23L then drain again, then add the final 13.44L and drain again?