I have that ruler set and love it! It is not hard, but like anything else it has a learning curve.My quilting is so much better with the rulers. Someone in an earlier post mentioned using a plain straight edge ruler, but that is not the same as the quilting rulers. The rulers in the set are made to a special thickness and used with a ruler foot so the ruler doesn't slide under the needle. Some of them have handles you hold onto as you move the ruler with the fabric.
They are a bit pricey, but worth it if you do your own FMQing on a domestic machine.