People tend to ignore my suggestion, but it works nicely for me. Whenever the snails are stupid enough to come near the front or side glass, out comes the fork and my Rams get a treat. I let the population stay steady, if for some reason I do get a population boom I pop in something green to attract them and take them out.
As for Assassin Snails, I can't see any reason why they wouldn't work. Like Dave says, if you've got massive numbers of snails add some Assassins and stop overfeeding (more importantly) theres no reason why it wouldn't settle down. If I didn't like my fork method so much I'd give it a punt-in fact I'm pretty sure a place I've just started shopping at sells them, so I might pick a couple up next time I'm down there.
Assassins won't feet on the shrimps, they eat algae and debris if they can't find snails.