Patchin inner tubes
ID hole, mark with cross-hairs if needed.
Roughen surface with sandpaper, for adhesion. Wipe clean.
Smear thin film of rubber solution larger than patch.
Wait until tacky; a bit dry but with some grab. Test it out on a spare inner.
Some people add another layer of rubber solution and wait till tacky.
Apply patch, pressing from centre outwards to exclude air.
Crease patch to break film or foil. Peel film from centre, outwards. NOT from edge, inwards.
Some people rub chalk dust over remaining tacky rubber to prevent sticking to tyre. I don't.

Patches with feathered of bevelled edges are best.