Watch the Las Palmas: Intro Section online guitar lesson by John Knowles, C.G.P. from Fingerstyle Journals
In the intro to "Las Palmas", I'm going for a bass line, which in a mariachi would be provided by a guitarrón...the harmony of two trumpets...and the rhythm of a guitar strumming up and down. To make the strumming work, I'm using my right middle finger to keep the spacing between index and ring, so that I can skip a string while strumming up and down...like one big finger with two fingertips.
I remember spending a little extra time working out the intro, like a practice loop. I would sing along so that the parts were clear. You're just about there when someone in the next room asks, "How much longer are you going to play the same thing over and over?"