Watch the I IV bIII bVI Etude Level 3 online guitar lesson by Vicki Genfan from Open Tuning Handbook: Rhythm
My first suggestion – slow it down! This etude requires you to change chords really quickly. You don't want this to sound sloppy...do you? Make sure your percussion hits are on + 4 of the measure. Have you found a nice bass drum and snare drum sound? Make sure to bang around (gently) on different areas of your guitar to find the best sonic hot-spots!