I have used Sketchup to make models for my 3D printer for a while. Sketchup is a very capable tool but it does have its limitations. Rounding edges and creating natural shapes are some of them.
Keeping with free software I decided to looking into Blender. Blender is a very powerful 3d modeling tool but has a steeper learning curve.
The following Video’s are a quick start to using Blender.
Working with some models…
Preparing items before 3d printing is also very important…