Yes you have to cut out dairy completely, it is really hard as it's hidden in alot of things you wouldn't expect it to be in (chicken gravy granules, salt and vinegar crisps etc). You have to check all ingredient lists for milk, milk protein, whey etc, luckily most things have milk on the allergin list these days but is better to double check.
Dd4 was fine for about a week after birth then she got a very fine rash on her face, was a dusky pink colour, slightly raised. The midwife said it was a heat rash as it was May 09 and it was very hot that month. Then the reflux started, just pain at first then bringing up bits of feeds and by 8 weeks she was screaming in agony whan laid flat, bringing up either milk or clear acidic fluid between feeds and most of her feeds coming up not long after, fussing while feeding, throwing herself back, fidgeting and coughing in her sleep, sudden screams etc. The doc said colic, I knew it wasn't, I've done colic and this wasn't it. Went to another doc who got covered in acidic milk sick and was given gaviscon. Only gave this for a few weeks before the severe constipation made me stop.
Some online mums on another parenting forum suggested trying dairy free to rule out dairy intollerance and I was willing to try anything as dd wasn't gaining weight at all. Cut the dairy and within a week the rash had cleared up and she wasn't in as much pain, within a month she was 100% better apart from when I accidentally ate anything with dairy in it (a few days later the rash and reflux would be back for a few days). She's 17 months now and we've just started trying her with some dairy, first cooked milk (lasagne etc) and she was fine so in the last week she's had a spoon of weetabix with milk and a little cheese on some spag bol and she's been fine so I think she's outgrowing it. We are still going to keep her at tastes only for a few more months just incase though.
When I said express I meant just to let the excess out, not a full express, I used to do this after dd1 & dd2 when I had oversupply and it didn't make my supply go up at all as I was just taking the edge off the engorgement, the same as letting it leak in the bath as an example (I used an electric pump set on the minimum suck pressure so it didn't simulate a baby feeding and once it was flowing I'd let it flow by itself and it would stop after a minute or so and gave some relief, was just enough to make the excess come off so baby could latch on (went from a B to a DD so the norks were too huge for baby to latch on when engorged).
I've bfed all four of mine and I haven't found anything to stop the strong letdown, it's hard when they are tiny but as they get bigger they can cope with the quicker milk flow so it doesn't cause as many issues. The letdown pain went away for me by the time they were all 3 months (apart from ds who was formula fed by then because my oversupply turned into no supply when I was expressing more than I was feeding due to being told 'give him some bottles' by interfering in-laws). I don't know whether it was me just getting used to the pain or that the flow slowed down a little by then but I could still shoot it 3m when baby unlatched unexpectedly, lol)