I second the assassin snail/ crushing as many of the pest snails as you can on a daily basis idea. Had a 55gal. overrun with pest snails, and between the assassins and crushing, the pests were gone in about a month.
If you have a spare tank, move fish. Clean tank with peroxide. Then set tank back up. You can also treat the plants with a lesser peroxide solution to rid them of all snails and eggs. Good luck. I've never had any luck with any fish or assassin snails. Getting rid of all of them. They do help for a little while.
Because I had 20 tanks, most in the 6 ft range, I had a certain fish that I would shuttle from tank to tank (its main tank was a 150 gal, and the cichlid was about 12" long).
It is Paretroplus maculatus, and could eradicate a fully snail infested tank within 24 hours, then be moved to another tank, and do it all over again.
In Madagascar its main source of food is/are snails. It can crush normal size Malay cone snails, but with its can opener like teeth, extract flesh from large snails with ease.
I do "not" recommend this fish unless your tank is at least 6 ft long.
An entire tank like the one below, with this kind of infestation, could be eliminated in 24 hours.