Watch the One - One - Two Forms online guitar lesson by Brad Carlton from Guitar Lab: The Golden Arp
The one-one-two form of the add 9 arpeggio in 1st inversion is the focus of this lesson. Though a stretched out form, this inversion is quite useful both in rhythm and lead applications. The lower two forms (starting on the 6th and 5th strings) do not require any finger position shifts. Begin by touching the 9 on the lowest string with your 4th finger, the 3 on the middle string with your 2nd, and the 5 on the highest string with your 1st finger. This forms a cluster (2-3-5) which is a great voicing for rhythm. Then simply add the root with your 4th finger on the highest string. That completes the arpeggio which can be played with sweep picking, finger picking, hybrid picking, alternate picking, and hammer-on pull-off moves. I'll address fingering options on all forms as well as dampening issues.