Ditto what Carl said and I use them with a small block of basswood against the sheetmetal bolster to spread side frames without any pressure or stress on the sintered side frame panels themselves. As far as KC weights go, I am not aware of a crimping tool, but loose ones can sometimes be addressed by closing the coupler, push the weight up into position, apply a tiny drop of CA at the point the pin goes into the weight, keep the coupler closed, apply a tiny drop of accelerator, hold closed a few more seconds, and release. (Be careful not to get any CA up into the channel for the pin or it will get glued into position.) Usually that holds pretty well. Some you have to clean first if they're greasy/dirty.
PS Once you get wheel sets gauged correctly, I clean the point of axle entry into the backs of wheels with 91% isopropyl on a cotton swab. Allow to dry, then work a small drop of CA around and into that union, sometimes followed by a tiny drop of accelerator. Helps keep gauging intact. They tend to creep in toward each other over time.
