I use stopflats2. They have an awesome lifetime guarantee. I was touring and at the end sent them two liners with 5 punctured tubes and they sent me 2 brand new liners and 5 brand new tubes to replace it. I should mention that I was using my crap stock tires instead of upgrading and the punctures I did receive were long and heavy duty nails.
Stopflats (not sure if tuffys have the same recommendation) advise to NOT cut or sand the liner. doing do will increase the chance of flats when the liner cuts through the tube. The liners come pre-tapered. I didnt use talc, stuck put them in and inflated. After a while, the liner sticks to the tire enough to not move but can still be removed with minimal effort.