I can attest that regular nipple suction does work.
I started as an A cup, then had to go up to a B, and now my B's are getting tight, so a C is in consideration for my next new bra!
I use nipple suckers when out and about, and to set me up for the breast pumps. I use an Ardo Calypso double electric pump at full throttle several times a day, with suitable lubricant.
I found it essential to epilate my breasts and nipples in order to get a good latch. I get sucked in by about 1 1/2 inches now.
After a pumping session, I am quite tender and heavy, so I use breast shells in my bra to protect my extended nipples.
My regime is: nipple suction, breast pumps, breast shells.....