If I have a shave with some irritation, then I'll use an alum block on the shaved areas. Just make sure to wash it off before applying any aftershaves.
If I get a nick, then I'll typically use a styptic pencil. I hold the styptic pencil on the nick for 5-10 seconds. It stops the bleeding every time.
These are the items I use:
Osma Alum
Clubman Styptic