loose IEC power cord connection?

It's not so much a question of the IEC connector fitting into the component. It's whether the connector grips firmly onto the component's prongs. Many connectors fall right back out and if that happens, no wrapping, etc. of ends is going to help make a firm electrical connection. This is the main reason I use Furutech IEC connectors when possible. They really grip.

Nothing applied to the outside of the IEC plug does a thing to improve its connectivity. Just keeps it from falling out.

Okay, but put a Furutech IEC connector on your power cord and I'll bet you can hear the difference :-)

This is assuming that you can do this without miswiring, electrocuting yourself, burning the place down, or otherwise wishing you hadn't.