How to age playing cards?
Work the cards. That would be the only way to make them seem used for a long time. 

What you would want to do is learn a few ways of shuffling (ie. overhand, riffling and cascading. There are tons of examples on the web.) No need to use any fancy techniques, just basic card handling. Then just constantly work the cards until they are broken in. 

It may take some time (maybe a day or two) but you can shuffle as you do other things. You just need to flex and rub the cards together for a length of time, concentrating the working of the cards over their lifetime into a few hours. That combined with the visual aging methods you describe will give the cards a used look and feel.