Do you have any experience doing so?

I have a project coming up where I would like to print a large object and fill it with sand and resin.

Sand, as we all know is coarse, rough and irritating and it gets everywhere. So it's good filler material.

Afterwards I want to solidify it by adding resin, hoping that it gets everywhere as well.

What other materials are usable? Perhaps concrete but it can't really dry inside a printed object right?

The infill should be Gyroid with 10% with at least 3 perimeters IMO. Would something like tree infill work as well? Or removable infill? I'm not sure how to get a slicer to do that though.

I intend to build parts for a CNC machine so I value weight and rigidity in this project.