modify an STL so that part of the print appears damaged

Hi, I am looking for a way to do this useing free software pls

I am creating a 'tail' to be used on a costume.

I have the full tail that I pulled from another model but I am scaling it up and cutting it in half.

This is so that the 'tail' is more manageable and fits the scale of the costume rather than the orig model. The orig is the Agisis face hugger by the way....

Anyhow, I want to modify one of the segments so that it appears to have been smashed and severed, I dont want to do this manually after print as it will show the infill etc and ruin the affect of the prop.

Does anyone know of a software that I can use to do that, I am NOT very good at design, I can run sketchup and make basic things, I can use Meshmixer to do plane cuts..

Thats about the limit of my skills, this is way beyond me so I am hoping there is something, a plug in maybe that can do what I need....

Thanx!

I found something that did the job.

I used Meshmixer to do a plane cut then used the sculpt tool and found under brushes a 'robustSmooth' brush that I could tune to disrupt the smooth surface perfectly for what I needed.