Do you mean vacuum pumps or lactation pumps?

I wrote quite detailed guide on vacuum pumping which you can easily find. I have more than two thousand hours done on vacuum pumps and close to eight hundred on lacatation pumps, so I might be able to help answer some questions.
But the main points with vacuum pumps are following: Never overdo it, use moderate pressure. You don't want to get insane tissue damage like how some poeple have got from ridiculous overpumping. Discolouration and dome edge marks can take months to heal, don't get to that point. Consistency is key with your program and more hours you get in, more results you will see. Its better to keep steady hours each day than do a marathon in one day. Use a belt to keep the cups together, you don't want them pushing your armpits and the sensitive area where there are ton of nerves as that could at worst cause nerve damage. Noogleberry is hands down the best pump you can easily find, well worth the money.