I've steam blocked a small quilt. Just hold your steam iron close to but not touching your quilt. Let the whole top get damp. You can then pin it to your ironing surface and let dry overnite, making sure the corners are square before pinning. This only works if your pinning surface is larger than the quilt. Most of the quilts I make are wallhangings, so I don't wash them ever. I want them to be flat.