Alex de Grassi defines cross string as “In third position or higher, it becomes possible to combine open and fretted strings to play ascending/descending intervals on non-sequential strings. This technique is called cross-string picking.” De Grassi, Alex, Cross-String Picking Basics, www.acousticguitar.com/cross-string-picking-basics/
DADGAD allows for many cross-string options due to the string tuning. A melody starts on the third or G string and then continues to the second or A open string followed by the third melodic note on the first string. Rather than having to stay on one string with cross-string you can use neighboring strings in your melody line.
The foundation of my new Hymns for DADGAD Guitar songbook now in final edit is based on cross-string technique in fingerstyle guitar. There are almost unlimited possibilities with the DADGAG tuning and cross-string to bring out the melody line using neighboring open and fretted strings all in one melodic set.
I will be providing a You-Tube video on cross string technique soon. Production has started on all YouTube Videos at Hillview Studios - July 2018!