I find that the fabric has enough stretch/give on it's own when I need to 'adjust' a block a bit to make it fit. I do press with steam during construction as well. I've not had a need to 'block' blocks.
That said, I've 'blocked' many a piece of needlepoint; cross stitch; knitting in my day. And yes, you must dampen/wet the piece; pin it in place; let dry thoroughly. For these pieces that usually means at least overnight or until the next time I have a chance to work with it.