Now when I was learning to sew, back in the stone age, I was taught to sew-press-sew-press and not to sew across a seam before it was pressed. I was also taught that pressing was an up and down motion with the iron. "Ironing" was a term for what you did after you got the clothes in off the line or out of the dryer. This was before permanent press. THAT is one of my favorite modern inventions!
Ironing is different than pressing. I learned to iron by watching my mother. She didn't have a nice fancy steam iron, so she used a sprinkler top on a bottle, sprinkling all the garments and folding and rolling them up. She put them in a plastic bag in the laundry basket, then started ironing the smaller pieces first, because they would dry out more quickly than the big ones.
My six brothers and my dad wore white shirts to church every Sunday. Those shirts needed ironing every single week. So did the five oxford-cloth dress shirts that Dad wore to work during the week. In addition we ironed our blouses and dresses, pillow cases and Dad's work pants. Believe me, I know how to iron!! My DD asked me how I learned, and I told her by watching my mom. She promptly covered her eyes!
I learned to press in my first sewing class in seventh grade. I can't remember the home ec teacher's name, but I do remember some of my experiences very well. I had to tear out a lapped zipper three times because I didn't do it her way, and she hated my blind hem (by hand, no less!!) That class put me off sewing for a while! If it wasn't for a friend of my mom's I probably would have stopped sewing completely by the end of ninth grade. But that's a blog for another day.
I learned to sew about age 10 or so on my grandma's treadle machine. Of course she thought I would burn my fingers on the iron, so the stuff I did was what we now call 'finger pressed'. But finally in home ec class, I was taught to press. Up and down, slide the iron as little as possible. The goal is to flatten an area without distorting it. Today's fabrics, with their blended fiber content and wrinkle resistance, are less in need firm ironing than light touching up. Lots of times, after prewashing a fabric, I find the only area that appears wrinkly could be the selvedge edges.
My fellow sewing guild members say they can tell who presses and who doesn't; that garments that were unpressed during construction look 'home-made', while garments using the press/sew methods look hand-made, or more like ready to wear.
When I sew garments, I sew/press/sew/press religiously. When I'm quilting, sometimes I finger press the small pieces, or use my 'Little Wooden Iron', or press a quantity of pieces after assembly line sewing them. But the point is, I still almost always press after each round of sewing. And I can tell right away when I break my own rules!
I'm not saying that anyone who doesn't PFF is wrong. There are always multiple ways to do almost anything. You have to find the right method for yourself. It's like a recipe book, use the ones you like that give you the results you want, and pass over the others. But if your projects are not turning out exactly the way you want them to, one thing to look at is whether your pressing techniques need a little tweeking. Try PFF, you might like it!