Here is a video of RYA Coach Assessor Elsa Chance getting underway in her Oppie in one of the Helford River Children's Sailing Trust's videos. The sequence for getting underway in a Mirror is fairly similar.
With a Mirror, I would suggest the taller, or the more experienced sailor remains outside the boat while the smaller or less experienced sailor climbs aboard and puts the daggerboard in the case (but rasied) and makes sure the rudder is partly down. Note while getting things ready, Elsa holds the boat about 1/3rd of the way back from the bow and with the wind coming partly over the front and partly over the side so the sail flaps away from the centreline of the boat. With a Mirror the person holding the boat should hold the boat just aft of the shroud.
