Load STL then scribble on it with sculpt tool, deform/smooth a few places, then export and print. Not bad.
Which software do you use to scribble ?
downloaded Cubify Sculpt trial http://cubify.com/sculpt
Check this out (free) :
Meshmixer and Blender are free software that would work well for this too
Thanks, yes, I use both of them regularly and wouldn’t be without them.