I've found that Tuffies are helpful. I've had mixed results with Slime.

I'd advise looking for the thickest, toughest tires you can find and adding Tuffies. I've never had a flat with my winter Nokian studded tires, for example. Most bike tires are optimized for light weight, not puncture resistance.

I have had flats caused by kevlar liners. If improperly installed, they can wear through the tube. However, I wouldn't leave home without them.

Paul