When I was a kid, we always patched our tubes by lighting the glue on fire. Always. Light it. Let it burn for a second our two - just to heat up the rubber - then apply the patch. I do not remember ever having a patch fail that way. Bicycle innertubes didn't exactly grow on trees in my neck of the woods in Maine back then, so we'd be riding patched tubes forever. I never heard of doing it any other way until I was a teen and started working in bike shops when our family moved to the mainland.