How To Be a Human Cow (lesson #1) -
Firstly paint black splotches over self, attach large bell around self's neck and rename self Daisy. Or Clover.
Secondly choose your milk pail. I use one of three, depending on the occasion. A bottle (sterilised of course which is annoying and boring and the main reason my breast pump is currently on sale at the local Help the Aged shop) if baby will be drinking it in the next few hours, one of the pre-sterilised (hazaah!) sealable breastmilk bags if it's going in the fridge or freezer, or a little bowl if you're expressing to make up baby rice or porridge.
Thirdly check that the curtains/blinds in the room you are expressing in are closed - very important unless you want to have your binman unexpectedly appear at the window, with facial expressions going from to to to .
Remove self's Milk Producer (the largest of the two) from storage. Check curtains/blinds really are shut.
Take aim - with the bottle and the bag I try to get as much of the nipple into it, with the bowl I just keep it close, or have it on the kitchen counter and lean into it. It's not that messy although if you take your eye off the task in hand and get all engrossed in Strictly Come Dancing you may find a fine shower on self's jeans / newspaper / computer keyboard / child.
Get into character with a nice big "Moooo" and then, holding the bit just outside the areola between the thumb and forefinger, squeeze. Repeat the "Moooo" if you're a Method Expresser. After a few you should get some milk, sometimes it's a constant flow, sometimes you have to keep on squeezing depending on how the milk reserves are. (It's worth it at this point to check the other Milk Producer as sometimes both cylinders fire up, which is always fun when you don't realise and then pop to the corner shop for the paper.)
And really that's pretty much it. I never had a manual or anything; I just started doing it one day after I'd thrown my breast pump across the room and Don't Call My Mummy Yummy was yelling for his daily porridge. Just have a go and see how you get on. I can usually get about 100oz in a bottle in 15 mins (supermoo). Once you get going you will wonder why you ever sterilised a breast pump. Just don't forget to remove the bell and black splotches once you're done.