Watch the C 6 add 9 Tuning online guitar lesson by Vicki Genfan from Essentials: Open Tunings
Notice how little my fingers (left hand) actually move between chords. Be sure you always leave fingers down that the next chord has in common. The less movement you have to make, the quicker you'll be able to master a smooth chord change. Also notice when my thumb comes up over the top of the neck to gently mute the low 6th string when I don't want to hear it (Asus chord). This makes it real easy for me to keep a full stringed, smooth strumming pattern going on.