There are any number of methods you can use. Your local box store can provide you with samples and paint, they sometimes hide them in the decorating section instead of the paint dept.
I like a combination of the crackle and brushed using the crackle lightly around edges and seams with a random splash here and there. Where you have to cut in you tend to go slower and apply more paint and it tends to crack over time. Brush the rest, usually a light color over a darker one. Makes it look like the paint has worn away over time.