I always pass the tyre round with my fingertips in an angled line across the inside of the tyre so that they catch on any protusion, and that works most of the time. The problem comes with thorns etc that don't protude in until the weight of the bike passes over them on the road, and I've never found a sure-fire solution to finding those.Sometimes I do struggle to find the offending object in the tyre though, and have on more than one occasion repaired or replaced the tube only to find it punctures shortly after because I didn't diagnose correctly the first time. I also use self adhesive patches rather than glue which shortens the process even more.
I have tried the self adhesive patches but on two occasions they've failed some while later, one of them becoming porous and letting air seep through the patch. It could have been the brand or batch at fault of course, but I prefer to stick to thin feathered edge patches as the most reliable of all and which never peel.
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