Ever tried these before? Insights? (Possible TMI)

Some time ago I found these on one of my favorite adult toy sites. My interest was piqued and I showed my fiance. Not long ago, he found the same thing on the wish app, got them to surprise me and try them out. They are nipple screws/clamps. They look more and allegedly feel more like a piercing than a clamp. I already like to play a little bit with clamps but have no experience with these. This past weekend we tried to use them the first time. We are experiencing difficulty actually getting my nipples in between the screws and winding them closed enough to stay on. Now for the TMI part, my nipples are nearly perfectly flat, even when stimulated. Usually when using other clamps I just work them up enough and then pull and clamp but these take a few seconds to work the screws down and more than one hand. I wanted to ask here if anyone has ever tried these or had similar difficulty and what worked for them. I tried prepping myself with my other clamps, I tried flicking myself for quite some time, I even got into the freezer and put ice on myself for a good long time. It felt great but I couldn't keep my flat little nipples out long enough to close my fun new clamps/screws on them. Any ideas or suggestions here or will this just take time to work up to?