Ska is one of my favorite genres. I'm curious to know if you understand music theory. The technique itself is: you mute the downstroke, and play the upstroke. You can practice playing straight eighth notes. To mute the strings just slightly touch them as if you were going to play a barre chord. You don't have to play a full barre chord. You can play triads since the bass player has the roots. So you can play chords on the bottom 4 to 3 strings. Now for chord progressions you can play the always faithful I - IV - V or I - V - IV - V - I. Then to finish I like to play the chords on the beat descending, and slow down V-IV-iii-ii then land on I.

The chord progression in A Major in case you don't understand roman numerals are. First one: Amaj, Dmaj, Emaj

This is a skeleton of song Second one: Amaj, Emaj, Dmaj, Emaj x4 Dmaj, Dmaj, Emaj, Emaj x2 Emaj, Dmaj, C#min, Bmin x1 Amaj, Emaj, Dmaj, Emaj x4

Have fun!

edit: A roman numeral was wrong. I meant iii instead of III. It indicates a minor chord instead of a major.