Here are some drills inspired by the song Imagine by John Lennon.
To play this drill, form an F chord using an E shape barre chord:
We won’t play all the notes in the chord, but it’s a nice idea to have the full chord fretted, just in case you hit an errant string.
On your picking hand, use your thumb to pick the F notes on the 1st fret of the low E string. Use your 1st finger to pick the notes on the A string, your 2nd finger to play the notes on the D string, and your 3rd finger to pick the notes on the G string. Notice on beats 1 and 3 we are playing the bottom 4 strings simultaneously. In beats 2 and 4 we omit the F on the low E. On on the upbeats we’ll hit that low F with our thumb to provide a bass pedal.
Start slowly and gradually build up speed: