There are many different types of shuffle rhythms available, and each one was 'purpose built' for a particular style of music. Note that your basic shuffle is often written as dotted 8th & 16th notes, but it's rarely played that way. Strict adherence to 1(e&)a 2(e&)a 3(e&)a 4(e&)a tends to sound mechanical or choppy, and just not swinging. Counting 1~uh 2~uh 3~uh 4~uh leaves you free to interpret and fine tune the feel of a shuffle. i