if you want your pieces to lay falt and match then you will press. prewashing is a matter of preference. some do and some dont. However, if you want to be sure all the chemicals are out of the fabric and they won't shrink or fade then you will pre wash. I don't consider these unnecesary steps to assure good results. Every quilting has his or her ways of doing things. You have to make up you mind how you will do it.