Regarding the double shots in battle, it is the same as Pendulum training. You gotta shake it 2-9 times depending on your digimon.
Like how it starts to give you a signal to shake/"Count" in Pendulum, it'll be the same thing before you enter the battle server/scan.
If you however did just that, where you get megahits in pendulum but not getting any in battles, then there is something wrong somewhere o.o
Read more: http://digimonunlimited.proboards.com/thread/188#ixzz2leBB77Gc