How should I protect trimmed wires in a push-in connector?
Wires can sometimes be worked out of a push-in connector by twisting and pulling. If the clipped wires cannot be removed because they're too short or won't pull out then replace the whole connector with a new push-on or twist connector.

The clipped wires are sure to have relatively sharp edges somewhere. Like any paint, it's easy to get a thick coating of liquid tape on a smooth surface but it's hard to make it build a good thickness on edges.