You might want to consider tougher tires and tire liners (flat sheet of material that is sandwiched between the tire and tube) since they prevent debris from getting to tube. They are reasonably light and not messy (like slime or other tube sealants). "Thorn proof" tubes are usually just thick wall inner tubes that may give you an extra millimeter of material, but seems like a few more rotation of a the object in the tube would eventually pierce the tube. Slime is a semi fluid gel that coats the internals of the tube, so any punctures would be sealed.

The number one defense should be preventing debris from penetrating the tire (consider Continental Gatorskins, Specialized Armadillos or Bontragers "Hardcsae" line of tires)
The second line of defense should be preventing debris from touching the tube (tire liners)