Years ago when all we had were tubulars, they use to make a U shape wire thing that fastened to the front brake just barely touching it, so that as you rode any thing you picked up on the tire the U thing would scrape it off before you rolled over it again puncturing the tire. I haven't seen this thing in years and can't even remembered what they called it, but it worked pretty good-way better then your hand, didn't prevent all flats but prevented most of them.