If ironing a piece of fabric you move the iron around over the fabric to get rid of wrinkles or to starch your fabric to help with accurate cuts. If you are (pressing) a pieced block you place the iron, lift reposition and place again. You do not move the iron around on a pieced block due to that stretching/distorting your blocks. Generally it only takes a few seconds in each area to press your blocks. If using steam (or starch) 2-3 seconds at a time should do the job