I would always suggest getting a corker! Saves a lot of time and headaches and the better one you get the easier it is. I got a floor corker and it takes a matter of about 2 seconds and it is in the correct depth and no damage to the cork.
The floor corkers run around 60-70 area and the hank corkers can run from 20 and up. Forcing the corks with things like mallets are dangerous and can damage the corks where they will not seal good.