Watch the Drop 2, 4 Voicings online guitar lesson by Brad Carlton from Guitar Lab: The Golden Arp
The 1st inversion drop 2, 4 voicing of the add 9 chord is effective in the higher registers more so than down low. That is because the 9(2) is the lowest voice. The form which involves the 5 4 2 1 string group is quite easy to play. Try playing it over a bass note (the root) to help discern the add 9 harmony. The voicing which resides on the 6 5 3 2 string group involves a barre with the 2nd finger. The video deals with all the technical issues.