38 weeks 3 days, practising hand expressing.help?

Hi breastfeeding mamas! I had a breastfeeding class today and we were shown a hand expressing technique, where you massage the breast, then squeeze with a c shape then release. I have tried practising this today and I wanted to know, how long do you massage for, should your breasts tingle or feel tender afterwards? Also I know breast stimulation can bring on labour, so if I feel any cramping or contractions I will stop immediately, I just wanted to practice what I was taught today, but had questions as a ftm. Thanks in advance for your help!