First centre the named star after finishing the dift aligning , go to the object menu , flick past deep sky, solar system etc until you get to named star . The stars are alphabetically set so youll have to scroll through them until you get the one you want {you can be more direct by entering their IC or other catalogue number}.Once found press enter , press and hold enter again for a couple of seconds until you here a beep , the screen should say the star has been syncyed . Should add just make sure the star is centered before syncing. After doing this pick another star and hit GOTO , centre that,sync it, and you should be set.
While i have no experiance with long exposures ive read 5 min is the min amount of time that should produce good results , i would go for ten minutes though . For 2 hrs doing some PEC training is going to be needed i think . Drift aligning should elimanate chances of field rotation , for imageing i would rely on drift aligning rather than then the Polar home alignment using sigma octanis.
Heres a pic depicting the Polar home position , just subsitute the north arrow with south for us {image taken form the excellent
www.MeadeLX200gps.com site}