Watch the Picking and Strumming online guitar lesson by Jesús Hernández from Buena Vista Cuban Guitar Guidebook
When using picking techniques, you mainly use the thumb to play on the D, A, and E string and the other fingers to play on the other strings. You have lots of options to combine the note you choose to play with the thumb and other fingers. You can play different intervals, as long as you play notes that belongs to the chord you are playing.
When strumming, we have multiple choices. We can accentuate the fourth beat or just avoid playing accents on any beat. You can play the body of the song using picking and in the montuno part of the song (where all improvisation happens). You can also do this the other way around.