I go on a snail killing spree every morning on my 2 planted tanks. I mash the ones on the glass but if I want to hit the mother-load I look under the drift wood. That's where most of them hang out. I mash every one. I have 3 types of snails in my tanks. Pond snails, ramshorn and a very small vertically flattend light colored snail that I have been unable it identify.
I have made a huge dent in the snail population simply by mashing them when I see them. It's an ongoing battle though. I'm sure that if I quit mashing snails for a couple of weeks I'll be overrun.