First pierce ur nipples then use weight, u will have big nipples
I have done this with one of my slaves aThis is a prime example of some of that thoughtless fantasy being suggested as real ideas. Newly pierced nipples need several months to properly heal even more so if you plan to use the piercings to hold weight. Even after all of that the only thing you will achieve will be stretched piercing holes as when one gauges the ear piercings.
To the OP:
Pumping, tugging, hormones, banding with tiny rubber bands and constant stimulation will help . Again do your research before attempting.