@nikv .I love the pots in the colour they already are, I wish I could find some like that over here, I would put them in my yard with some herbs like you have or maybe some of them petunias I have growing. :D
I would have gone the same way as you, tapping them with a rubber mallet is the safest way to go.
I once used a normal hammer and a towel to tap some cups my wife had stuck and they popped out fine.
Why don't you set up a self watering system for the pots, you can do it with a two litter bottle and some air line, I am going to do a post one day about the one I made for the green house, if you do it right you just need to fill the bottle once a week and your plants will be happier for it.
happy days. :D