Hi Wooly, I am no expert in the 3D printing game, but I am going to stick my head on the block here and expect an axe swing at any time but here goes ...

Bump will not work as it does not alter geometry of the mesh, and is a render time effect where light intensity dictates height or depth of the "grain" or texture.

Displacement mapping does actually alter the geometry of the object , but again this is render time applied and does not display on the model being worked on.

Sculpture type modelling is available in Blender where you should be able to apply a texture to the brush and this will then translate to the model, however as a beginner i would say you would need lots of practice. Once you have that mastered then you would have to export to a format suitable for 3D printing.

The final option is to model the texture directly on to a surface within MoI. If its a grain or skin/fur effect then that is tedious and resource hungry with NURBS - If it's a simple tyre thread kind of texture then you can model it, but again it will be resource hungry.

HTH ...

Martin