The number one mistake people usually make with moles is not what they use, but where they use it. Whatever preventative or poison you use needs to be done in this manner.
You will see two types of mole tunnels. Some will look like a maze with tunnels everywhere. These are feeder tunnels and the mole is most likely NOT going to travel through these a second time..unfortunatly these tunnels are most often the ones that people focus on, thinking they are the most active.Ignore these and look for:
THE LONE TUNNEL.. this one stretches over a long distance adn is usually all by itself. This is a travel tunnel and needs to be the one focused on. Whatever means you use as long as you focus on these tunnelss you will have as much success as possible, by this I mean ocassionally you will have to deal with these critters again.
Also...to quell your fears regarding numbers... moles are very territorial and will always be few in numbers, regardless of what it looks like
Happy Hunting