I'm not entirely sure what you're asking... are you asking how to get rid of the snails or how to not hurt them while you're vacuuming?
If you want to get rid of them, you can put a piece of cucumber in the tank overnight... the next morning, you should have a bunch of snails on it when you take it out. They really don't hurt anything though, so it doesn't hurt anything to leave them in the tank. If they are overpopulated, you can just feed the tank less, so there's less extra food around for the snails to eat.
If you're asking how to not hurt them while you vacuum... just vacuum as usual, and let the old tank water sit in the bucket for a few minutes before you dump it. By that time, the snails that got vacuumed up will have a hold on the side of the bucket and will stay stuck while the water is dumped... then you can just pluck them out and put them back. I'm not sure why you'd want to cycle, since you already have fish in the tank, unless you mean a fish-in cycle and that is just more water changes anyways.