Try practicing this basic polyrhythm! A polyrhythm is just what it sounds like - more than one rhythm juxtaposed on top of one another. A warning: while this may seem simple in concept, pulling it off is no easy feat! Try practicing with two people at first, one on each part. Then see if you can master it solo!
Practice a simplified version of the Dembow riddim, a rhythm with roots in Jamaica that has more recently been popularized by the Reggaeton genre. Play it solo, or with a friend!
In music we often group ideas together into relatively small, repeatable sections. These groups are called measures (because we "measured" out how long it is). In this case, we put the four strikes of the milk jug in a measure (1, 2, 3, 4) along with the eight shakes of the grain bag (1, 2, 3, 4, 5, 6, 7, 8). Try following along with the pattern presented here, alternating a measure of 4 milk jug strikes with a measure of 4 milk jug strikes + 8 grain bag shakes. It's harder than it looks!