Here's a bench we painted using the same technique. The first coat was painted with General Finishes Milk Paint in Brick Red (using a paint brush with lots of random brush strokes). Next a layer of blue (a custom color mix of Milk Paint colors) was scraped over the bench. Finally a layer of Patina Green Milk Paint was scraped over the bench. Each scraped layer is uneven and lets some of the previous colors show through.
Wouldn't this bench look great in your yard? The matching end table (shown in the picture below) was painted the same way. No sanding necessary!