stopping your thoughts takes very little effort in comparison with visualization or whatever. It's just that you are not used to doing nothing. You think that you are always obliged to do something to achieve your goal but try doing nothing. It's much easier! The only thing that keeps our consciousness in this world is the inner talk. Stop it and open yourself to other realms. When a though appears stop it, when the next one appears, again stop it and don't worry about the result, it's just about "stopping".