Besides the expensive tire liners like Mr Tuffy or SpinSkins, as an "eco friendly", re-cyclable alternative, you may want to try using a discarded tire in reasonable condition, the same size as your bike's tires, as a "liner". You'd want a smooth tread, no mountain bike tire treads. Then you CAREFULLY cut the bead off of the tire using whatever sharp tool works best for you. Some type of shears or scissors should work well. Then you can insert the trimmed tire carcass between the tube and tire and put the tire back on your wheel with the extra protection inside. Of course this "tire liner" will give some extra protection from the ordinary punctures you may get, and even protects the sidewall better, but it's no Mr Tuffy. It is usually free though, and that is a plus when you're "experimenting!" Most bike shops will gladly give you the old worn out tires in your size. Just be sure to ask for them.