You forgot the fourth major ingredient, which is sanding off the mould-release compound that coats the outside of the tube before applying the glue. If you don't do this, the patch WILL fail.

Either Rema or Park Tools patch kits are really good. So-called "glueless" patches are worthless unless having the patch fail at some indeterminate time is OK with you. It only adds about two minutes of time to use a proper vulcanizing patch kit. I always carry a patch kit in addition to at least one spare tube because flats usually come in threes. Similar to canklecat , if the hole location is obvious I will often just pull out that section of tube and apply a patch instead of the more time consuming changeout of the tube.

Much to the amusement of my riding buddies, I will keep adding patches to a tube until the point of ridiculousness and sometimes beyond. I think this stems from my paper route teen years when I didn't want to spend the money on tubes (or ride all the way to the bike shop to get them). With vulcanizing patches the repair is as strong as the tube so the only functional reason not to add patches it the miniscule amount of weight it might add to the wheel.