The intro to Pinball Wizard is a pretty easy set of chords that use a few open strings to fill out the melody. The basic technique is just using downstrokes, hitting 3 or 4 strings on the 1st beat then keeping a steady flow of eighth notes through the rest of the measure.
When the faster strumming starts you keep a steady flow of sixteenth notes, alternating downs and ups but accenting every third stroke, rather than the more common every fourth stroke. I recommend practicing this with an easier chord than the Bsus4 (barred at the 7th fret)- an open E chord might be good.
Here is a pdf of the TAB and the video.






